diff --git a/handlers/bootstrap.go b/handlers/bootstrap.go
index cb8252f..9e8e90b 100644
--- a/handlers/bootstrap.go
+++ b/handlers/bootstrap.go
@@ -3,11 +3,12 @@ package handlers
 import (
 	"log"
 	"os"
-	"time"
 
 	"github.com/docker/docker/client"
+	"github.com/play-with-docker/play-with-docker/config"
 	"github.com/play-with-docker/play-with-docker/docker"
 	"github.com/play-with-docker/play-with-docker/pwd"
+	"github.com/play-with-docker/play-with-docker/storage"
 )
 
 var core pwd.PWDApi
@@ -28,16 +29,11 @@ func Bootstrap() {
 
 	t := pwd.NewScheduler(Broadcast, d)
 
-	s := pwd.NewStorage()
-
-	core = pwd.NewPWD(d, t, Broadcast, s)
-
-	loadStart := time.Now()
-	err = core.SessionLoadAndPrepare()
-	loadElapsed := time.Since(loadStart)
-	log.Printf("***************** Loading stored sessions took %s\n", loadElapsed)
+	s, err := storage.NewFileStorage(config.SessionsFile)
 
 	if err != nil && !os.IsNotExist(err) {
 		log.Fatal("Error decoding sessions from disk ", err)
 	}
+	core = pwd.NewPWD(d, t, Broadcast, s)
+
 }
diff --git a/pwd/check_swarm_status_task.go b/pwd/check_swarm_status_task.go
index 3019a27..8f0ee94 100644
--- a/pwd/check_swarm_status_task.go
+++ b/pwd/check_swarm_status_task.go
@@ -4,16 +4,17 @@ import (
 	"log"
 
 	"github.com/docker/docker/api/types/swarm"
+	"github.com/play-with-docker/play-with-docker/pwd/types"
 )
 
 type checkSwarmStatusTask struct {
 }
 
-func (c checkSwarmStatusTask) Run(i *Instance) error {
-	if i.docker == nil {
+func (c checkSwarmStatusTask) Run(i *types.Instance) error {
+	if i.Docker == nil {
 		return nil
 	}
-	if info, err := i.docker.GetDaemonInfo(); err == nil {
+	if info, err := i.Docker.GetDaemonInfo(); err == nil {
 		if info.Swarm.LocalNodeState != swarm.LocalNodeStateInactive && info.Swarm.LocalNodeState != swarm.LocalNodeStateLocked {
 			i.IsManager = &info.Swarm.ControlAvailable
 		} else {
diff --git a/pwd/check_swarm_used_ports.go b/pwd/check_swarm_used_ports.go
index 7157240..a62dd05 100644
--- a/pwd/check_swarm_used_ports.go
+++ b/pwd/check_swarm_used_ports.go
@@ -3,27 +3,29 @@ package pwd
 import (
 	"fmt"
 	"log"
+
+	"github.com/play-with-docker/play-with-docker/pwd/types"
 )
 
 type checkSwarmUsedPortsTask struct {
 }
 
-func (c checkSwarmUsedPortsTask) Run(i *Instance) error {
-	if i.docker == nil {
+func (c checkSwarmUsedPortsTask) Run(i *types.Instance) error {
+	if i.Docker == nil {
 		return nil
 	}
 	if i.IsManager != nil && *i.IsManager {
-		sessionPrefix := i.session.Id[:8]
+		sessionPrefix := i.Session.Id[:8]
 		// This is a swarm manager instance, then check for ports
-		if hosts, ports, err := i.docker.GetSwarmPorts(); err != nil {
+		if hosts, ports, err := i.Docker.GetSwarmPorts(); err != nil {
 			log.Println(err)
 			return err
 		} else {
 			for _, host := range hosts {
 				host = fmt.Sprintf("%s_%s", sessionPrefix, host)
 				for _, port := range ports {
-					if i.session.Instances[host] != nil {
-						i.session.Instances[host].setUsedPort(port)
+					if i.Session.Instances[host] != nil {
+						i.Session.Instances[host].SetUsedPort(port)
 					}
 				}
 			}
diff --git a/pwd/check_used_ports_task.go b/pwd/check_used_ports_task.go
index 74e3f3b..83ffb89 100644
--- a/pwd/check_used_ports_task.go
+++ b/pwd/check_used_ports_task.go
@@ -1,17 +1,21 @@
 package pwd
 
-import "log"
+import (
+	"log"
+
+	"github.com/play-with-docker/play-with-docker/pwd/types"
+)
 
 type checkUsedPortsTask struct {
 }
 
-func (c checkUsedPortsTask) Run(i *Instance) error {
-	if i.docker == nil {
+func (c checkUsedPortsTask) Run(i *types.Instance) error {
+	if i.Docker == nil {
 		return nil
 	}
-	if ports, err := i.docker.GetPorts(); err == nil {
+	if ports, err := i.Docker.GetPorts(); err == nil {
 		for _, p := range ports {
-			i.setUsedPort(uint16(p))
+			i.SetUsedPort(uint16(p))
 		}
 	} else {
 		log.Println(err)
diff --git a/pwd/client.go b/pwd/client.go
index f50d758..6fc1021 100644
--- a/pwd/client.go
+++ b/pwd/client.go
@@ -3,51 +3,42 @@ package pwd
 import (
 	"log"
 	"time"
+
+	"github.com/play-with-docker/play-with-docker/pwd/types"
 )
 
-type Client struct {
-	Id       string
-	viewPort ViewPort
-	session  *Session
-}
-
-type ViewPort struct {
-	Rows uint
-	Cols uint
-}
-
-func (p *pwd) ClientNew(id string, session *Session) *Client {
+func (p *pwd) ClientNew(id string, session *types.Session) *types.Client {
 	defer observeAction("ClientNew", time.Now())
-	c := &Client{Id: id, session: session}
-	session.clients = append(session.clients, c)
+	c := &types.Client{Id: id, Session: session}
+	session.Clients = append(session.Clients, c)
 	return c
 }
 
-func (p *pwd) ClientResizeViewPort(c *Client, cols, rows uint) {
+func (p *pwd) ClientResizeViewPort(c *types.Client, cols, rows uint) {
 	defer observeAction("ClientResizeViewPort", time.Now())
-	c.viewPort.Rows = rows
-	c.viewPort.Cols = cols
+	c.ViewPort.Rows = rows
+	c.ViewPort.Cols = cols
 
-	p.notifyClientSmallestViewPort(c.session)
+	p.notifyClientSmallestViewPort(c.Session)
 }
 
-func (p *pwd) ClientClose(client *Client) {
+func (p *pwd) ClientClose(client *types.Client) {
 	defer observeAction("ClientClose", time.Now())
 	// Client has disconnected. Remove from session and recheck terminal sizes.
-	session := client.session
-	for i, cl := range session.clients {
+	session := client.Session
+	for i, cl := range session.Clients {
 		if cl.Id == client.Id {
-			session.clients = append(session.clients[:i], session.clients[i+1:]...)
+			session.Clients = append(session.Clients[:i], session.Clients[i+1:]...)
 			break
 		}
 	}
-	if len(session.clients) > 0 {
+	if len(session.Clients) > 0 {
 		p.notifyClientSmallestViewPort(session)
 	}
-	setGauges()
+	p.setGauges()
 }
 
-func (p *pwd) notifyClientSmallestViewPort(session *Session) {
+func (p *pwd) notifyClientSmallestViewPort(session *types.Session) {
 	vp := p.SessionGetSmallestViewPort(session)
 	// Resize all terminals in the session
 	p.broadcast.BroadcastTo(session.Id, "viewport resize", vp.Cols, vp.Rows)
diff --git a/pwd/client_test.go b/pwd/client_test.go
index 4aed04a..7ab9243 100644
--- a/pwd/client_test.go
+++ b/pwd/client_test.go
@@ -4,6 +4,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/play-with-docker/play-with-docker/pwd/types"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -20,8 +21,8 @@ func TestClientNew(t *testing.T) {
 
 	client := p.ClientNew("foobar", session)
 
-	assert.Equal(t, Client{Id: "foobar", session: session, viewPort: ViewPort{Cols: 0, Rows: 0}}, *client)
-	assert.Contains(t, session.clients, client)
+	assert.Equal(t, types.Client{Id: "foobar", Session: session, ViewPort: types.ViewPort{Cols: 0, Rows: 0}}, *client)
+	assert.Contains(t, session.Clients, client)
 }
 
 func TestClientResizeViewPort(t *testing.T) {
@@ -49,7 +50,7 @@ func TestClientResizeViewPort(t *testing.T) {
 
 	p.ClientResizeViewPort(client, 80, 24)
 
-	assert.Equal(t, ViewPort{Cols: 80, Rows: 24}, client.viewPort)
+	assert.Equal(t, types.ViewPort{Cols: 80, Rows: 24}, client.ViewPort)
 	assert.Equal(t, session.Id, broadcastedSessionId)
 	assert.Equal(t, "viewport resize", broadcastedEventName)
 	assert.Equal(t, uint(80), broadcastedArgs[0])
diff --git a/pwd/collect_stats_task.go b/pwd/collect_stats_task.go
index 200c35c..828d190 100644
--- a/pwd/collect_stats_task.go
+++ b/pwd/collect_stats_task.go
@@ -5,9 +5,10 @@ import (
 	"fmt"
 	"log"
 
-	"github.com/docker/docker/api/types"
+	dockerTypes "github.com/docker/docker/api/types"
 	units "github.com/docker/go-units"
 	"github.com/play-with-docker/play-with-docker/docker"
+	"github.com/play-with-docker/play-with-docker/pwd/types"
 )
 
 type collectStatsTask struct {
@@ -22,14 +23,14 @@ type collectStatsTask struct {
 	docker docker.DockerApi
 }
 
-func (c collectStatsTask) Run(i *Instance) error {
+func (c collectStatsTask) Run(i *types.Instance) error {
 	reader, err := c.docker.GetContainerStats(i.Name)
 	if err != nil {
 		log.Println("Error while trying to collect instance stats", err)
 		return err
 	}
 	dec := json.NewDecoder(reader)
-	var v *types.StatsJSON
+	var v *dockerTypes.StatsJSON
 	e := dec.Decode(&v)
 	if e != nil {
 		log.Println("Error while trying to collect instance stats", e)
@@ -53,7 +54,7 @@ func (c collectStatsTask) Run(i *Instance) error {
 	return nil
 }
 
-func calculateCPUPercentUnix(previousCPU, previousSystem uint64, v *types.StatsJSON) float64 {
+func calculateCPUPercentUnix(previousCPU, previousSystem uint64, v *dockerTypes.StatsJSON) float64 {
 	var (
 		cpuPercent = 0.0
 		// calculate the change for the cpu usage of the container in between readings
diff --git a/pwd/instance.go b/pwd/instance.go
index e0807f5..c0abe36 100644
--- a/pwd/instance.go
+++ b/pwd/instance.go
@@ -1,19 +1,17 @@
 package pwd
 
 import (
-	"context"
 	"fmt"
 	"io"
 	"log"
-	"net"
 	"net/http"
 	"path/filepath"
 	"strings"
-	"sync"
 	"time"
 
 	"github.com/play-with-docker/play-with-docker/config"
 	"github.com/play-with-docker/play-with-docker/docker"
+	"github.com/play-with-docker/play-with-docker/pwd/types"
 
 	"golang.org/x/text/encoding"
 )
@@ -29,35 +27,6 @@ func (s *sessionWriter) Write(p []byte) (n int, err error) {
 	return len(p), nil
 }
 
-type UInt16Slice []uint16
-
-func (p UInt16Slice) Len() int           { return len(p) }
-func (p UInt16Slice) Less(i, j int) bool { return p[i] < p[j] }
-func (p UInt16Slice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
-
-type Instance struct {
-	Image        string           `json:"image"`
-	Name         string           `json:"name"`
-	Hostname     string           `json:"hostname"`
-	IP           string           `json:"ip"`
-	IsManager    *bool            `json:"is_manager"`
-	Mem          string           `json:"mem"`
-	Cpu          string           `json:"cpu"`
-	Alias        string           `json:"alias"`
-	ServerCert   []byte           `json:"server_cert"`
-	ServerKey    []byte           `json:"server_key"`
-	CACert       []byte           `json:"ca_cert"`
-	Cert         []byte           `json:"cert"`
-	Key          []byte           `json:"key"`
-	IsDockerHost bool             `json:"is_docker_host"`
-	session      *Session         `json:"-"`
-	conn         net.Conn         `json:"-"`
-	ctx          context.Context  `json:"-"`
-	docker       docker.DockerApi `json:"-"`
-	tempPorts    []uint16         `json:"-"`
-	Ports        UInt16Slice
-	rw           sync.Mutex
-}
 type InstanceConfig struct {
 	ImageName  string
 	Alias      string
@@ -70,32 +39,12 @@ type InstanceConfig struct {
 	Host       string
 }
 
-func (i *Instance) setUsedPort(port uint16) {
-	i.rw.Lock()
-	defer i.rw.Unlock()
-
-	for _, p := range i.tempPorts {
-		if p == port {
-			return
-		}
-	}
-	i.tempPorts = append(i.tempPorts, port)
-}
-func (i *Instance) IsConnected() bool {
-	return i.conn != nil
-
-}
-
-func (i *Instance) SetSession(s *Session) {
-	i.session = s
-}
-
-func (p *pwd) InstanceResizeTerminal(instance *Instance, rows, cols uint) error {
+func (p *pwd) InstanceResizeTerminal(instance *types.Instance, rows, cols uint) error {
 	defer observeAction("InstanceResizeTerminal", time.Now())
 	return p.docker.ContainerResize(instance.Name, rows, cols)
 }
 
-func (p *pwd) InstanceAttachTerminal(instance *Instance) error {
+func (p *pwd) InstanceAttachTerminal(instance *types.Instance) error {
 	conn, err := p.docker.CreateAttachConnection(instance.Name)
 
 	if err != nil {
@@ -103,14 +52,14 @@ func (p *pwd) InstanceAttachTerminal(instance *Instance) error {
 	}
 
 	encoder := encoding.Replacement.NewEncoder()
-	sw := &sessionWriter{sessionId: instance.session.Id, instanceName: instance.Name, broadcast: p.broadcast}
-	instance.conn = conn
+	sw := &sessionWriter{sessionId: instance.Session.Id, instanceName: instance.Name, broadcast: p.broadcast}
+	instance.Terminal = conn
 	io.Copy(encoder.Writer(sw), conn)
 
 	return nil
 }
 
-func (p *pwd) InstanceUploadFromUrl(instance *Instance, url string) error {
+func (p *pwd) InstanceUploadFromUrl(instance *types.Instance, url string) error {
 	defer observeAction("InstanceUploadFromUrl", time.Now())
 	log.Printf("Downloading file [%s]\n", url)
 	resp, err := http.Get(url)
@@ -133,41 +82,34 @@ func (p *pwd) InstanceUploadFromUrl(instance *Instance, url string) error {
 	return nil
 }
 
-func (p *pwd) InstanceGet(session *Session, name string) *Instance {
+func (p *pwd) InstanceGet(session *types.Session, name string) *types.Instance {
 	defer observeAction("InstanceGet", time.Now())
 	return session.Instances[name]
 }
 
-func (p *pwd) InstanceFindByIP(ip string) *Instance {
+func (p *pwd) InstanceFindByIP(ip string) *types.Instance {
 	defer observeAction("InstanceFindByIP", time.Now())
-	for _, s := range sessions {
-		for _, i := range s.Instances {
-			if i.IP == ip {
-				return i
-			}
-		}
+	i, err := p.storage.InstanceFindByIP(ip)
+	if err != nil {
+		return nil
 	}
-	return nil
+
+	return i
 }
 
-func (p *pwd) InstanceFindByAlias(sessionPrefix, alias string) *Instance {
+func (p *pwd) InstanceFindByAlias(sessionPrefix, alias string) *types.Instance {
 	defer observeAction("InstanceFindByAlias", time.Now())
-	for id, s := range sessions {
-		if strings.HasPrefix(id, sessionPrefix) {
-			for _, i := range s.Instances {
-				if i.Alias == alias {
-					return i
-				}
-			}
-		}
+	i, err := p.storage.InstanceFindByAlias(sessionPrefix, alias)
+	if err != nil {
+		return nil
 	}
-	return nil
+	return i
 }
 
-func (p *pwd) InstanceDelete(session *Session, instance *Instance) error {
+func (p *pwd) InstanceDelete(session *types.Session, instance *types.Instance) error {
 	defer observeAction("InstanceDelete", time.Now())
-	if instance.conn != nil {
-		instance.conn.Close()
+	if instance.Terminal != nil {
+		instance.Terminal.Close()
 	}
 	err := p.docker.DeleteContainer(instance.Name)
 	if err != nil && !strings.Contains(err.Error(), "No such container") {
@@ -178,16 +120,16 @@ func (p *pwd) InstanceDelete(session *Session, instance *Instance) error {
 	p.broadcast.BroadcastTo(session.Id, "delete instance", instance.Name)
 
 	delete(session.Instances, instance.Name)
-	if err := p.storage.Save(); err != nil {
+	if err := p.storage.SessionPut(session); err != nil {
 		return err
 	}
 
-	setGauges()
+	p.setGauges()
 
 	return nil
 }
 
-func (p *pwd) checkHostnameExists(session *Session, hostname string) bool {
+func (p *pwd) checkHostnameExists(session *types.Session, hostname string) bool {
 	containerName := fmt.Sprintf("%s_%s", session.Id[:8], hostname)
 	exists := false
 	for _, instance := range session.Instances {
@@ -199,10 +141,10 @@ func (p *pwd) checkHostnameExists(session *Session, hostname string) bool {
 	return exists
 }
 
-func (p *pwd) InstanceNew(session *Session, conf InstanceConfig) (*Instance, error) {
+func (p *pwd) InstanceNew(session *types.Session, conf InstanceConfig) (*types.Instance, error) {
 	defer observeAction("InstanceNew", time.Now())
-	session.rw.Lock()
-	defer session.rw.Unlock()
+	session.Lock()
+	defer session.Unlock()
 
 	if conf.ImageName == "" {
 		conf.ImageName = config.GetDindImageName()
@@ -247,7 +189,7 @@ func (p *pwd) InstanceNew(session *Session, conf InstanceConfig) (*Instance, err
 		return nil, err
 	}
 
-	instance := &Instance{}
+	instance := &types.Instance{}
 	instance.Image = opts.Image
 	instance.IP = ip
 	instance.Name = containerName
@@ -258,33 +200,33 @@ func (p *pwd) InstanceNew(session *Session, conf InstanceConfig) (*Instance, err
 	instance.ServerCert = conf.ServerCert
 	instance.ServerKey = conf.ServerKey
 	instance.CACert = conf.CACert
-	instance.session = session
+	instance.Session = session
 	// For now this condition holds through. In the future we might need a more complex logic.
 	instance.IsDockerHost = opts.Privileged
 
 	if session.Instances == nil {
-		session.Instances = make(map[string]*Instance)
+		session.Instances = make(map[string]*types.Instance)
 	}
 	session.Instances[instance.Name] = instance
 
 	go p.InstanceAttachTerminal(instance)
 
-	err = p.storage.Save()
+	err = p.storage.SessionPut(session)
 	if err != nil {
 		return nil, err
 	}
 
 	p.broadcast.BroadcastTo(session.Id, "new instance", instance.Name, instance.IP, instance.Hostname)
 
-	setGauges()
+	p.setGauges()
 
 	return instance, nil
 }
 
-func (p *pwd) InstanceWriteToTerminal(instance *Instance, data string) {
+func (p *pwd) InstanceWriteToTerminal(instance *types.Instance, data string) {
 	defer observeAction("InstanceWriteToTerminal", time.Now())
-	if instance != nil && instance.conn != nil && len(data) > 0 {
-		instance.conn.Write([]byte(data))
+	if instance != nil && instance.Terminal != nil && len(data) > 0 {
+		instance.Terminal.Write([]byte(data))
 	}
 }
 
@@ -298,7 +240,7 @@ func (p *pwd) InstanceAllowedImages() []string {
 
 }
 
-func (p *pwd) InstanceExec(instance *Instance, cmd []string) (int, error) {
+func (p *pwd) InstanceExec(instance *types.Instance, cmd []string) (int, error) {
 	defer observeAction("InstanceExec", time.Now())
 	return p.docker.Exec(instance.Name, cmd)
 }
diff --git a/pwd/instance_test.go b/pwd/instance_test.go
index a97e1b8..ea7270e 100644
--- a/pwd/instance_test.go
+++ b/pwd/instance_test.go
@@ -8,6 +8,7 @@ import (
 
 	"github.com/play-with-docker/play-with-docker/config"
 	"github.com/play-with-docker/play-with-docker/docker"
+	"github.com/play-with-docker/play-with-docker/pwd/types"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -31,7 +32,7 @@ func TestInstanceResizeTerminal(t *testing.T) {
 
 	p := NewPWD(docker, tasks, broadcast, storage)
 
-	err := p.InstanceResizeTerminal(&Instance{Name: "foobar"}, 24, 80)
+	err := p.InstanceResizeTerminal(&types.Instance{Name: "foobar"}, 24, 80)
 
 	assert.Nil(t, err)
 	assert.Equal(t, "foobar", resizedInstanceName)
@@ -61,14 +62,14 @@ func TestInstanceNew(t *testing.T) {
 
 	assert.Nil(t, err)
 
-	expectedInstance := Instance{
+	expectedInstance := types.Instance{
 		Name:         fmt.Sprintf("%s_node1", session.Id[:8]),
 		Hostname:     "node1",
 		IP:           "10.0.0.1",
 		Alias:        "",
 		Image:        config.GetDindImageName(),
 		IsDockerHost: true,
-		session:      session,
+		Session:      session,
 	}
 
 	assert.Equal(t, expectedInstance, *instance)
@@ -107,8 +108,8 @@ func TestInstanceNew_Concurrency(t *testing.T) {
 
 	assert.Nil(t, err)
 
-	var instance1 *Instance
-	var instance2 *Instance
+	var instance1 *types.Instance
+	var instance2 *types.Instance
 
 	wg := sync.WaitGroup{}
 	wg.Add(2)
@@ -152,14 +153,14 @@ func TestInstanceNew_WithNotAllowedImage(t *testing.T) {
 
 	assert.Nil(t, err)
 
-	expectedInstance := Instance{
+	expectedInstance := types.Instance{
 		Name:         fmt.Sprintf("%s_node1", session.Id[:8]),
 		Hostname:     "node1",
 		IP:           "10.0.0.1",
 		Alias:        "",
 		Image:        "redis",
 		IsDockerHost: false,
-		session:      session,
+		Session:      session,
 	}
 
 	assert.Equal(t, expectedInstance, *instance)
@@ -200,14 +201,14 @@ func TestInstanceNew_WithCustomHostname(t *testing.T) {
 
 	assert.Nil(t, err)
 
-	expectedInstance := Instance{
+	expectedInstance := types.Instance{
 		Name:         fmt.Sprintf("%s_redis-master", session.Id[:8]),
 		Hostname:     "redis-master",
 		IP:           "10.0.0.1",
 		Alias:        "",
 		Image:        "redis",
 		IsDockerHost: false,
-		session:      session,
+		Session:      session,
 	}
 
 	assert.Equal(t, expectedInstance, *instance)
diff --git a/pwd/pwd.go b/pwd/pwd.go
index 124bd06..f0c3a1c 100644
--- a/pwd/pwd.go
+++ b/pwd/pwd.go
@@ -1,10 +1,11 @@
 package pwd
 
 import (
-	"sync"
 	"time"
 
 	"github.com/play-with-docker/play-with-docker/docker"
+	"github.com/play-with-docker/play-with-docker/pwd/types"
+	"github.com/play-with-docker/play-with-docker/storage"
 	"github.com/prometheus/client_golang/prometheus"
 )
 
@@ -33,65 +34,58 @@ func observeAction(action string, start time.Time) {
 	latencyHistogramVec.WithLabelValues(action).Observe(float64(time.Since(start).Nanoseconds()) / 1000000)
 }
 
-var sessions map[string]*Session
-var sessionsMutex sync.Mutex
-
 func init() {
 	prometheus.MustRegister(sessionsGauge)
 	prometheus.MustRegister(clientsGauge)
 	prometheus.MustRegister(instancesGauge)
 	prometheus.MustRegister(latencyHistogramVec)
-
-	sessions = make(map[string]*Session)
 }
 
 type pwd struct {
 	docker    docker.DockerApi
 	tasks     SchedulerApi
 	broadcast BroadcastApi
-	storage   StorageApi
+	storage   storage.StorageApi
 }
 
 type PWDApi interface {
-	SessionNew(duration time.Duration, stack string, stackName, imageName string) (*Session, error)
-	SessionClose(session *Session) error
-	SessionGetSmallestViewPort(session *Session) ViewPort
-	SessionDeployStack(session *Session) error
-	SessionGet(id string) *Session
-	SessionLoadAndPrepare() error
-	SessionSetup(session *Session, conf SessionSetupConf) error
+	SessionNew(duration time.Duration, stack string, stackName, imageName string) (*types.Session, error)
+	SessionClose(session *types.Session) error
+	SessionGetSmallestViewPort(session *types.Session) types.ViewPort
+	SessionDeployStack(session *types.Session) error
+	SessionGet(id string) *types.Session
+	SessionSetup(session *types.Session, conf SessionSetupConf) error
 
-	InstanceNew(session *Session, conf InstanceConfig) (*Instance, error)
-	InstanceResizeTerminal(instance *Instance, cols, rows uint) error
-	InstanceAttachTerminal(instance *Instance) error
-	InstanceUploadFromUrl(instance *Instance, url string) error
-	InstanceGet(session *Session, name string) *Instance
-	InstanceFindByIP(ip string) *Instance
-	InstanceFindByAlias(sessionPrefix, alias string) *Instance
-	InstanceDelete(session *Session, instance *Instance) error
-	InstanceWriteToTerminal(instance *Instance, data string)
+	InstanceNew(session *types.Session, conf InstanceConfig) (*types.Instance, error)
+	InstanceResizeTerminal(instance *types.Instance, cols, rows uint) error
+	InstanceAttachTerminal(instance *types.Instance) error
+	InstanceUploadFromUrl(instance *types.Instance, url string) error
+	InstanceGet(session *types.Session, name string) *types.Instance
+	InstanceFindByIP(ip string) *types.Instance
+	InstanceFindByAlias(sessionPrefix, alias string) *types.Instance
+	InstanceDelete(session *types.Session, instance *types.Instance) error
+	InstanceWriteToTerminal(instance *types.Instance, data string)
 	InstanceAllowedImages() []string
-	InstanceExec(instance *Instance, cmd []string) (int, error)
+	InstanceExec(instance *types.Instance, cmd []string) (int, error)
 
-	ClientNew(id string, session *Session) *Client
-	ClientResizeViewPort(client *Client, cols, rows uint)
-	ClientClose(client *Client)
+	ClientNew(id string, session *types.Session) *types.Client
+	ClientResizeViewPort(client *types.Client, cols, rows uint)
+	ClientClose(client *types.Client)
 }
 
-func NewPWD(d docker.DockerApi, t SchedulerApi, b BroadcastApi, s StorageApi) *pwd {
+func NewPWD(d docker.DockerApi, t SchedulerApi, b BroadcastApi, s storage.StorageApi) *pwd {
 	return &pwd{docker: d, tasks: t, broadcast: b, storage: s}
 }
 
-func setGauges() {
-	var ins float64
-	var cli float64
-
-	for _, s := range sessions {
-		ins += float64(len(s.Instances))
-		cli += float64(len(s.clients))
-	}
+func (p *pwd) setGauges() {
+	s, _ := p.storage.SessionCount()
+	ses := float64(s)
+	i, _ := p.storage.InstanceCount()
+	ins := float64(i)
+	c, _ := p.storage.ClientCount()
+	cli := float64(c)
 
 	clientsGauge.Set(cli)
 	instancesGauge.Set(ins)
-	sessionsGauge.Set(float64(len(sessions)))
+	sessionsGauge.Set(ses)
 }
diff --git a/pwd/session.go b/pwd/session.go
index e584dc4..74026c7 100644
--- a/pwd/session.go
+++ b/pwd/session.go
@@ -11,6 +11,7 @@ import (
 
 	"github.com/play-with-docker/play-with-docker/config"
 	"github.com/play-with-docker/play-with-docker/docker"
+	"github.com/play-with-docker/play-with-docker/pwd/types"
 	"github.com/twinj/uuid"
 )
 
@@ -35,32 +36,12 @@ type SessionSetupInstanceConf struct {
 	IsSwarmWorker  bool   `json:"is_swarm_worker"`
 }
 
-type Session struct {
-	rw           sync.Mutex
-	Id           string               `json:"id"`
-	Instances    map[string]*Instance `json:"instances"`
-	CreatedAt    time.Time            `json:"created_at"`
-	ExpiresAt    time.Time            `json:"expires_at"`
-	PwdIpAddress string               `json:"pwd_ip_address"`
-	Ready        bool                 `json:"ready"`
-	Stack        string               `json:"stack"`
-	StackName    string               `json:"stack_name"`
-	ImageName    string               `json:"image_name"`
-	closingTimer *time.Timer          `json:"-"`
-	scheduled    bool                 `json:"-"`
-	clients      []*Client            `json:"-"`
-	ticker       *time.Ticker         `json:"-"`
-}
-
-func (p *pwd) SessionNew(duration time.Duration, stack, stackName, imageName string) (*Session, error) {
+func (p *pwd) SessionNew(duration time.Duration, stack, stackName, imageName string) (*types.Session, error) {
 	defer observeAction("SessionNew", time.Now())
 
-	sessionsMutex.Lock()
-	defer sessionsMutex.Unlock()
-
-	s := &Session{}
+	s := &types.Session{}
 	s.Id = uuid.NewV4().String()
-	s.Instances = map[string]*Instance{}
+	s.Instances = map[string]*types.Instance{}
 	s.CreatedAt = time.Now()
 	s.ExpiresAt = s.CreatedAt.Add(duration)
 	s.Ready = true
@@ -88,24 +69,24 @@ func (p *pwd) SessionNew(duration time.Duration, stack, stackName, imageName str
 		return nil, err
 	}
 
-	sessions[s.Id] = s
-	if err := p.storage.Save(); err != nil {
+	if err := p.storage.SessionPut(s); err != nil {
 		log.Println(err)
 		return nil, err
 	}
 
-	setGauges()
+	p.setGauges()
 
 	return s, nil
 }
 
-func (p *pwd) SessionClose(s *Session) error {
-	s.rw.Lock()
-	defer s.rw.Unlock()
+func (p *pwd) SessionClose(s *types.Session) error {
+	defer observeAction("SessionClose", time.Now())
+
+	s.Lock()
+	defer s.Unlock()
+
+	s.StopTicker()
 
-	if s.ticker != nil {
-		s.ticker.Stop()
-	}
 	p.broadcast.BroadcastTo(s.Id, "session end")
 	p.broadcast.BroadcastTo(s.Id, "disconnect")
 	log.Printf("Starting clean up of session [%s]\n", s.Id)
@@ -130,32 +111,35 @@ func (p *pwd) SessionClose(s *Session) error {
 			return err
 		}
 	}
-	delete(sessions, s.Id)
 
-	// We store sessions as soon as we delete one
-	if err := p.storage.Save(); err != nil {
+	err := p.storage.SessionDelete(s.Id)
+	if err != nil {
 		return err
 	}
-	setGauges()
+
 	log.Printf("Cleaned up session [%s]\n", s.Id)
+	p.setGauges()
 	return nil
 
 }
 
-func (p *pwd) SessionGetSmallestViewPort(s *Session) ViewPort {
-	minRows := s.clients[0].viewPort.Rows
-	minCols := s.clients[0].viewPort.Cols
+func (p *pwd) SessionGetSmallestViewPort(s *types.Session) types.ViewPort {
+	defer observeAction("SessionGetSmallestViewPort", time.Now())
 
-	for _, c := range s.clients {
-		minRows = uint(math.Min(float64(minRows), float64(c.viewPort.Rows)))
-		minCols = uint(math.Min(float64(minCols), float64(c.viewPort.Cols)))
+	minRows := s.Clients[0].ViewPort.Rows
+	minCols := s.Clients[0].ViewPort.Cols
+
+	for _, c := range s.Clients {
+		minRows = uint(math.Min(float64(minRows), float64(c.ViewPort.Rows)))
+		minCols = uint(math.Min(float64(minCols), float64(c.ViewPort.Cols)))
 	}
 
-	return ViewPort{Rows: minRows, Cols: minCols}
+	return types.ViewPort{Rows: minRows, Cols: minCols}
 }
 
-func (p *pwd) SessionDeployStack(s *Session) error {
+func (p *pwd) SessionDeployStack(s *types.Session) error {
 	defer observeAction("SessionDeployStack", time.Now())
+
 	if s.Ready {
 		// a stack was already deployed on this session, just ignore
 		return nil
@@ -188,60 +172,28 @@ func (p *pwd) SessionDeployStack(s *Session) error {
 	log.Printf("Stack execution finished with code %d\n", code)
 	s.Ready = true
 	p.broadcast.BroadcastTo(s.Id, "session ready", true)
-	if err := p.storage.Save(); err != nil {
+	if err := p.storage.SessionPut(s); err != nil {
 		return err
 	}
 	return nil
 }
 
-func (p *pwd) SessionGet(sessionId string) *Session {
+func (p *pwd) SessionGet(sessionId string) *types.Session {
 	defer observeAction("SessionGet", time.Now())
-	s := sessions[sessionId]
+
+	s, _ := p.storage.SessionGet(sessionId)
+
+	if err := p.prepareSession(s); err != nil {
+		log.Println(err)
+		return nil
+	}
 	return s
 }
 
-func (p *pwd) SessionLoadAndPrepare() error {
-	defer observeAction("SessionLoadAndPrepare", time.Now())
-	err := p.storage.Load()
-	if err != nil {
-		return err
-	}
-
-	wg := sync.WaitGroup{}
-	for _, s := range sessions {
-		// Connect PWD daemon to the new network
-		if s.PwdIpAddress == "" {
-			log.Printf("Cannot load store session [%s] as they don't have the pwd ip address stored with them\n", s.Id)
-			continue
-		}
-		wg.Add(1)
-		go func(s *Session) {
-			s.rw.Lock()
-			defer s.rw.Unlock()
-			defer wg.Done()
-
-			err := p.prepareSession(s)
-			if err != nil {
-				log.Println(err)
-			}
-			for _, i := range s.Instances {
-				// wire the session back to the instance
-				i.session = s
-				go p.InstanceAttachTerminal(i)
-			}
-		}(s)
-	}
-
-	wg.Wait()
-	setGauges()
-
-	return nil
-}
-
-func (p *pwd) SessionSetup(session *Session, conf SessionSetupConf) error {
+func (p *pwd) SessionSetup(session *types.Session, conf SessionSetupConf) error {
 	defer observeAction("SessionSetup", time.Now())
 	var tokens *docker.SwarmTokens = nil
-	var firstSwarmManager *Instance = nil
+	var firstSwarmManager *types.Instance = nil
 
 	// first look for a swarm manager and create it
 	for _, conf := range conf.Instances {
@@ -254,14 +206,14 @@ func (p *pwd) SessionSetup(session *Session, conf SessionSetupConf) error {
 			if err != nil {
 				return err
 			}
-			if i.docker == nil {
+			if i.Docker == nil {
 				dock, err := p.docker.New(i.IP, i.Cert, i.Key)
 				if err != nil {
 					return err
 				}
-				i.docker = dock
+				i.Docker = dock
 			}
-			tkns, err := i.docker.SwarmInit()
+			tkns, err := i.Docker.SwarmInit()
 			if err != nil {
 				return err
 			}
@@ -290,13 +242,13 @@ func (p *pwd) SessionSetup(session *Session, conf SessionSetupConf) error {
 				}
 				if c.IsSwarmManager || c.IsSwarmWorker {
 					// check if we have connection to the daemon, if not, create it
-					if i.docker == nil {
+					if i.Docker == nil {
 						dock, err := p.docker.New(i.IP, i.Cert, i.Key)
 						if err != nil {
 							log.Println(err)
 							return
 						}
-						i.docker = dock
+						i.Docker = dock
 					}
 				}
 
@@ -304,7 +256,7 @@ func (p *pwd) SessionSetup(session *Session, conf SessionSetupConf) error {
 					if c.IsSwarmManager {
 						// this is a swarm manager
 						// cluster has already been initiated, join as manager
-						err := i.docker.SwarmJoin(fmt.Sprintf("%s:2377", firstSwarmManager.IP), tokens.Manager)
+						err := i.Docker.SwarmJoin(fmt.Sprintf("%s:2377", firstSwarmManager.IP), tokens.Manager)
 						if err != nil {
 							log.Println(err)
 							return
@@ -312,7 +264,7 @@ func (p *pwd) SessionSetup(session *Session, conf SessionSetupConf) error {
 					}
 					if c.IsSwarmWorker {
 						// this is a swarm worker
-						err := i.docker.SwarmJoin(fmt.Sprintf("%s:2377", firstSwarmManager.IP), tokens.Worker)
+						err := i.Docker.SwarmJoin(fmt.Sprintf("%s:2377", firstSwarmManager.IP), tokens.Worker)
 						if err != nil {
 							log.Println(err)
 							return
@@ -330,7 +282,14 @@ func (p *pwd) SessionSetup(session *Session, conf SessionSetupConf) error {
 // This function should be called any time a session needs to be prepared:
 // 1. Like when it is created
 // 2. When it was loaded from storage
-func (p *pwd) prepareSession(session *Session) error {
+func (p *pwd) prepareSession(session *types.Session) error {
+	session.Lock()
+	defer session.Unlock()
+
+	if session.IsPrepared() {
+		return nil
+	}
+
 	p.scheduleSessionClose(session)
 
 	// Connect PWD daemon to the new network
@@ -341,17 +300,24 @@ func (p *pwd) prepareSession(session *Session) error {
 	// Schedule periodic tasks
 	p.tasks.Schedule(session)
 
+	for _, i := range session.Instances {
+		// wire the session back to the instance
+		i.Session = session
+		go p.InstanceAttachTerminal(i)
+	}
+	session.SetPrepared()
+
 	return nil
 }
 
-func (p *pwd) scheduleSessionClose(s *Session) {
+func (p *pwd) scheduleSessionClose(s *types.Session) {
 	timeLeft := s.ExpiresAt.Sub(time.Now())
-	s.closingTimer = time.AfterFunc(timeLeft, func() {
+	s.SetClosingTimer(time.AfterFunc(timeLeft, func() {
 		p.SessionClose(s)
-	})
+	}))
 }
 
-func (p *pwd) connectToNetwork(s *Session) error {
+func (p *pwd) connectToNetwork(s *types.Session) error {
 	ip, err := p.docker.ConnectNetwork(config.PWDContainerName, s.Id, s.PwdIpAddress)
 	if err != nil {
 		log.Println("ERROR NETWORKING")
diff --git a/pwd/session_test.go b/pwd/session_test.go
index 5432cc2..bef5a1d 100644
--- a/pwd/session_test.go
+++ b/pwd/session_test.go
@@ -2,24 +2,21 @@ package pwd
 
 import (
 	"fmt"
-	"net"
-	"sync"
 	"testing"
 	"time"
 
 	"github.com/play-with-docker/play-with-docker/config"
 	"github.com/play-with-docker/play-with-docker/docker"
+	"github.com/play-with-docker/play-with-docker/pwd/types"
 	"github.com/stretchr/testify/assert"
 )
 
 func TestSessionNew(t *testing.T) {
-	sessions = map[string]*Session{}
-
 	config.PWDContainerName = "pwd"
 	var connectContainerName, connectNetworkName, connectIP string
 	createdNetworkId := ""
 	saveCalled := false
-	expectedSessions := map[string]*Session{}
+	expectedSessions := map[string]*types.Session{}
 
 	docker := &mockDocker{}
 	docker.createNetwork = func(id string) error {
@@ -33,15 +30,15 @@ func TestSessionNew(t *testing.T) {
 		return "10.0.0.1", nil
 	}
 
-	var scheduledSession *Session
+	var scheduledSession *types.Session
 	tasks := &mockTasks{}
-	tasks.schedule = func(s *Session) {
+	tasks.schedule = func(s *types.Session) {
 		scheduledSession = s
 	}
 
 	broadcast := &mockBroadcast{}
 	storage := &mockStorage{}
-	storage.save = func() error {
+	storage.sessionPut = func(s *types.Session) error {
 		saveCalled = true
 		return nil
 	}
@@ -72,7 +69,7 @@ func TestSessionNew(t *testing.T) {
 	assert.Equal(t, "imageName", s.ImageName)
 	assert.False(t, s.Ready)
 
-	assert.NotNil(t, s.closingTimer)
+	assert.NotNil(t, s.ClosingTimer())
 
 	assert.Equal(t, config.PWDContainerName, connectContainerName)
 	assert.Equal(t, s.Id, connectNetworkName)
@@ -82,7 +79,6 @@ func TestSessionNew(t *testing.T) {
 
 	assert.Equal(t, s, scheduledSession)
 
-	assert.Equal(t, expectedSessions, sessions)
 	assert.True(t, saveCalled)
 }
 
@@ -208,72 +204,72 @@ func TestSessionSetup(t *testing.T) {
 
 	manager1 := fmt.Sprintf("%s_manager1", s.Id[:8])
 	manager1Received := *s.Instances[manager1]
-	assert.Equal(t, Instance{
+	assert.Equal(t, types.Instance{
 		Name:         manager1,
 		Image:        "franela/dind",
 		Hostname:     "manager1",
 		IP:           "10.0.0.1",
 		Alias:        "",
 		IsDockerHost: true,
-		session:      s,
-		conn:         manager1Received.conn,
-		docker:       manager1Received.docker,
+		Session:      s,
+		Terminal:     manager1Received.Terminal,
+		Docker:       manager1Received.Docker,
 	}, manager1Received)
 
 	manager2 := fmt.Sprintf("%s_manager2", s.Id[:8])
 	manager2Received := *s.Instances[manager2]
-	assert.Equal(t, Instance{
+	assert.Equal(t, types.Instance{
 		Name:         manager2,
 		Image:        "franela/dind",
 		Hostname:     "manager2",
 		IP:           "10.0.0.2",
 		Alias:        "",
 		IsDockerHost: true,
-		session:      s,
-		conn:         manager2Received.conn,
-		docker:       manager2Received.docker,
+		Session:      s,
+		Terminal:     manager2Received.Terminal,
+		Docker:       manager2Received.Docker,
 	}, manager2Received)
 
 	manager3 := fmt.Sprintf("%s_manager3", s.Id[:8])
 	manager3Received := *s.Instances[manager3]
-	assert.Equal(t, Instance{
+	assert.Equal(t, types.Instance{
 		Name:         manager3,
 		Image:        "franela/dind:overlay2-dev",
 		Hostname:     "manager3",
 		IP:           "10.0.0.3",
 		Alias:        "",
 		IsDockerHost: true,
-		session:      s,
-		conn:         manager3Received.conn,
-		docker:       manager3Received.docker,
+		Session:      s,
+		Terminal:     manager3Received.Terminal,
+		Docker:       manager3Received.Docker,
 	}, manager3Received)
 
 	worker1 := fmt.Sprintf("%s_worker1", s.Id[:8])
 	worker1Received := *s.Instances[worker1]
-	assert.Equal(t, Instance{
+	assert.Equal(t, types.Instance{
 		Name:         worker1,
 		Image:        "franela/dind",
 		Hostname:     "worker1",
 		IP:           "10.0.0.4",
 		Alias:        "",
 		IsDockerHost: true,
-		session:      s,
-		conn:         worker1Received.conn,
-		docker:       worker1Received.docker,
+		Session:      s,
+		Terminal:     worker1Received.Terminal,
+		Docker:       worker1Received.Docker,
 	}, worker1Received)
 
 	other := fmt.Sprintf("%s_other", s.Id[:8])
 	otherReceived := *s.Instances[other]
-	assert.Equal(t, Instance{
+	assert.Equal(t, types.Instance{
 		Name:         other,
 		Image:        "franela/dind",
 		Hostname:     "other",
 		IP:           "10.0.0.5",
 		Alias:        "",
 		IsDockerHost: true,
-		session:      s,
-		conn:         otherReceived.conn,
-		docker:       otherReceived.docker,
+		Session:      s,
+		Terminal:     otherReceived.Terminal,
+		Docker:       otherReceived.Docker,
 	}, otherReceived)
 
 	assert.True(t, swarmInitOnMaster1)
@@ -281,100 +277,3 @@ func TestSessionSetup(t *testing.T) {
 	assert.True(t, manager3JoinedHasManager)
 	assert.True(t, worker1JoinedHasWorker)
 }
-
-func TestSessionLoadAndPrepare(t *testing.T) {
-	config.PWDContainerName = "pwd"
-	lock := sync.Mutex{}
-	var s1NetworkConnect []string
-	var s2NetworkConnect []string
-
-	wg := sync.WaitGroup{}
-	wg.Add(3)
-	connectedInstances := []string{}
-	sessions = map[string]*Session{}
-	i1 := &Instance{
-		Image:        "dind",
-		Name:         "session1_i1",
-		Hostname:     "i1",
-		IP:           "10.0.0.10",
-		IsDockerHost: true,
-	}
-	i2 := &Instance{
-		Image:        "dind",
-		Name:         "session1_i2",
-		Hostname:     "i1",
-		IP:           "10.0.0.11",
-		IsDockerHost: true,
-	}
-	i3 := &Instance{
-		Image:        "dind",
-		Name:         "session1_i3",
-		Hostname:     "i1",
-		IP:           "10.0.0.12",
-		IsDockerHost: true,
-	}
-	s1 := &Session{
-		Id:           "session1",
-		Instances:    map[string]*Instance{"session1_i1": i1},
-		CreatedAt:    time.Now(),
-		ExpiresAt:    time.Now().Add(time.Hour),
-		PwdIpAddress: "10.0.0.1",
-		Ready:        true,
-		Stack:        "",
-		StackName:    "",
-	}
-	s2 := &Session{
-		Id:           "session2",
-		Instances:    map[string]*Instance{"session1_i2": i2, "session1_i3": i3},
-		CreatedAt:    time.Now(),
-		ExpiresAt:    time.Now().Add(time.Hour),
-		PwdIpAddress: "10.0.0.2",
-		Ready:        true,
-		Stack:        "",
-		StackName:    "",
-	}
-
-	dock := &mockDocker{}
-	dock.createAttachConnection = func(instanceName string) (net.Conn, error) {
-		lock.Lock()
-		defer lock.Unlock()
-		connectedInstances = append(connectedInstances, instanceName)
-		wg.Done()
-		return &mockConn{}, nil
-	}
-	dock.connectNetwork = func(container, network, ip string) (string, error) {
-		if s1.Id == network {
-			s1NetworkConnect = []string{container, network, ip}
-		} else if s2.Id == network {
-			s2NetworkConnect = []string{container, network, ip}
-		}
-		return ip, nil
-	}
-	tasks := &mockTasks{}
-	tasks.schedule = func(s *Session) {
-		s.ticker = time.NewTicker(1 * time.Second)
-	}
-	broadcast := &mockBroadcast{}
-	storage := &mockStorage{}
-
-	storage.load = func() error {
-		sessions = map[string]*Session{"session1": s1, "session2": s2}
-		return nil
-	}
-
-	p := NewPWD(dock, tasks, broadcast, storage)
-
-	err := p.SessionLoadAndPrepare()
-	assert.Nil(t, err)
-	assert.Len(t, sessions, 2)
-	assert.NotNil(t, s1.closingTimer)
-	assert.NotNil(t, s2.closingTimer)
-	assert.NotNil(t, s1.ticker)
-	assert.NotNil(t, s2.ticker)
-
-	assert.Equal(t, []string{"pwd", s1.Id, s1.PwdIpAddress}, s1NetworkConnect)
-	assert.Equal(t, []string{"pwd", s2.Id, s2.PwdIpAddress}, s2NetworkConnect)
-
-	wg.Wait()
-	assert.Subset(t, connectedInstances, []string{i1.Name, i2.Name, i3.Name})
-}
diff --git a/pwd/storage.go b/pwd/storage.go
deleted file mode 100644
index e3b2509..0000000
--- a/pwd/storage.go
+++ /dev/null
@@ -1,50 +0,0 @@
-package pwd
-
-import (
-	"encoding/gob"
-	"os"
-	"sync"
-
-	"github.com/play-with-docker/play-with-docker/config"
-)
-
-type StorageApi interface {
-	Save() error
-	Load() error
-}
-
-type storage struct {
-	rw sync.Mutex
-}
-
-func (store *storage) Load() error {
-	file, err := os.Open(config.SessionsFile)
-
-	if err == nil {
-		decoder := gob.NewDecoder(file)
-		err = decoder.Decode(&sessions)
-
-		if err != nil {
-			return err
-		}
-	}
-
-	file.Close()
-	return nil
-}
-
-func (store *storage) Save() error {
-	store.rw.Lock()
-	defer store.rw.Unlock()
-	file, err := os.Create(config.SessionsFile)
-	if err == nil {
-		encoder := gob.NewEncoder(file)
-		err = encoder.Encode(&sessions)
-	}
-	file.Close()
-	return nil
-}
-
-func NewStorage() *storage {
-	return &storage{}
-}
diff --git a/pwd/storage_mock_test.go b/pwd/storage_mock_test.go
index 197c8f2..d9d5d73 100644
--- a/pwd/storage_mock_test.go
+++ b/pwd/storage_mock_test.go
@@ -1,19 +1,63 @@
 package pwd
 
+import "github.com/play-with-docker/play-with-docker/pwd/types"
+
 type mockStorage struct {
-	save func() error
-	load func() error
+	sessionGet          func(sessionId string) (*types.Session, error)
+	sessionPut          func(s *types.Session) error
+	sessionCount        func() (int, error)
+	sessionDelete       func(sessionId string) error
+	instanceFindByAlias func(sessionPrefix, alias string) (*types.Instance, error)
+	instanceFindByIP    func(ip string) (*types.Instance, error)
+	instanceCount       func() (int, error)
+	clientCount         func() (int, error)
 }
 
-func (m *mockStorage) Save() error {
-	if m.save != nil {
-		return m.save()
+func (m *mockStorage) SessionGet(sessionId string) (*types.Session, error) {
+	if m.sessionGet != nil {
+		return m.sessionGet(sessionId)
+	}
+	return nil, nil
+}
+func (m *mockStorage) SessionPut(s *types.Session) error {
+	if m.sessionPut != nil {
+		return m.sessionPut(s)
 	}
 	return nil
 }
-func (m *mockStorage) Load() error {
-	if m.load != nil {
-		return m.load()
+func (m *mockStorage) SessionCount() (int, error) {
+	if m.sessionCount != nil {
+		return m.sessionCount()
+	}
+	return 0, nil
+}
+func (m *mockStorage) SessionDelete(sessionId string) error {
+	if m.sessionDelete != nil {
+		return m.sessionDelete(sessionId)
 	}
 	return nil
 }
+func (m *mockStorage) InstanceFindByAlias(sessionPrefix, alias string) (*types.Instance, error) {
+	if m.instanceFindByAlias != nil {
+		return m.instanceFindByAlias(sessionPrefix, alias)
+	}
+	return nil, nil
+}
+func (m *mockStorage) InstanceFindByIP(ip string) (*types.Instance, error) {
+	if m.instanceFindByIP != nil {
+		return m.instanceFindByIP(ip)
+	}
+	return nil, nil
+}
+func (m *mockStorage) InstanceCount() (int, error) {
+	if m.instanceCount != nil {
+		return m.instanceCount()
+	}
+	return 0, nil
+}
+func (m *mockStorage) ClientCount() (int, error) {
+	if m.clientCount != nil {
+		return m.clientCount()
+	}
+	return 0, nil
+}
diff --git a/pwd/tasks.go b/pwd/tasks.go
index 2b8ae57..adc52ce 100644
--- a/pwd/tasks.go
+++ b/pwd/tasks.go
@@ -15,15 +15,16 @@ import (
 	"github.com/docker/docker/client"
 	"github.com/docker/go-connections/tlsconfig"
 	"github.com/play-with-docker/play-with-docker/docker"
+	"github.com/play-with-docker/play-with-docker/pwd/types"
 )
 
 type periodicTask interface {
-	Run(i *Instance) error
+	Run(i *types.Instance) error
 }
 
 type SchedulerApi interface {
-	Schedule(session *Session)
-	Unschedule(session *Session)
+	Schedule(session *types.Session)
+	Unschedule(session *types.Session)
 }
 
 type scheduler struct {
@@ -31,21 +32,20 @@ type scheduler struct {
 	periodicTasks []periodicTask
 }
 
-func (sch *scheduler) Schedule(s *Session) {
-	if s.scheduled {
+func (sch *scheduler) Schedule(s *types.Session) {
+	if s.IsPrepared() {
 		return
 	}
 
 	go func() {
-		s.scheduled = true
-
-		s.ticker = time.NewTicker(1 * time.Second)
-		for range s.ticker.C {
+		t := time.NewTicker(1 * time.Second)
+		s.SetTicker(t)
+		for range t.C {
 			var wg = sync.WaitGroup{}
 			wg.Add(len(s.Instances))
 			for _, ins := range s.Instances {
-				var i *Instance = ins
-				if i.docker == nil && i.IsDockerHost {
+				var i *types.Instance = ins
+				if i.Docker == nil && i.IsDockerHost {
 					// Need to create client to the DinD docker daemon
 
 					// We check if the client needs to use TLS
@@ -76,7 +76,7 @@ func (sch *scheduler) Schedule(s *Session) {
 					if err != nil {
 						log.Println("Could not connect to DinD docker daemon", err)
 					} else {
-						i.docker = docker.NewDocker(c)
+						i.Docker = docker.NewDocker(c)
 					}
 				}
 				go func() {
@@ -98,17 +98,17 @@ func (sch *scheduler) Schedule(s *Session) {
 			wg.Wait()
 			// broadcast all information
 			for _, ins := range s.Instances {
-				ins.Ports = UInt16Slice(ins.tempPorts)
+				ins.Ports = types.UInt16Slice(ins.GetUsedPorts())
 				sort.Sort(ins.Ports)
-				ins.tempPorts = []uint16{}
+				ins.CleanUsedPorts()
 
-				sch.broadcast.BroadcastTo(ins.session.Id, "instance stats", ins.Name, ins.Mem, ins.Cpu, ins.IsManager, ins.Ports)
+				sch.broadcast.BroadcastTo(ins.Session.Id, "instance stats", ins.Name, ins.Mem, ins.Cpu, ins.IsManager, ins.Ports)
 			}
 		}
 	}()
 }
 
-func (sch *scheduler) Unschedule(s *Session) {
+func (sch *scheduler) Unschedule(s *types.Session) {
 }
 
 func NewScheduler(b BroadcastApi, d docker.DockerApi) *scheduler {
diff --git a/pwd/tasks_mock_test.go b/pwd/tasks_mock_test.go
index e990c61..b184349 100644
--- a/pwd/tasks_mock_test.go
+++ b/pwd/tasks_mock_test.go
@@ -1,16 +1,18 @@
 package pwd
 
+import "github.com/play-with-docker/play-with-docker/pwd/types"
+
 type mockTasks struct {
-	schedule   func(s *Session)
-	unschedule func(s *Session)
+	schedule   func(s *types.Session)
+	unschedule func(s *types.Session)
 }
 
-func (m *mockTasks) Schedule(s *Session) {
+func (m *mockTasks) Schedule(s *types.Session) {
 	if m.schedule != nil {
 		m.schedule(s)
 	}
 }
-func (m *mockTasks) Unschedule(s *Session) {
+func (m *mockTasks) Unschedule(s *types.Session) {
 	if m.unschedule != nil {
 		m.unschedule(s)
 	}
diff --git a/pwd/types/client.go b/pwd/types/client.go
new file mode 100644
index 0000000..2e31e5e
--- /dev/null
+++ b/pwd/types/client.go
@@ -0,0 +1,12 @@
+package types
+
+type Client struct {
+	Id       string
+	ViewPort ViewPort
+	Session  *Session
+}
+
+type ViewPort struct {
+	Rows uint
+	Cols uint
+}
diff --git a/pwd/types/instance.go b/pwd/types/instance.go
new file mode 100644
index 0000000..b39f60e
--- /dev/null
+++ b/pwd/types/instance.go
@@ -0,0 +1,63 @@
+package types
+
+import (
+	"context"
+	"net"
+	"sync"
+
+	"github.com/play-with-docker/play-with-docker/docker"
+)
+
+type UInt16Slice []uint16
+
+func (p UInt16Slice) Len() int           { return len(p) }
+func (p UInt16Slice) Less(i, j int) bool { return p[i] < p[j] }
+func (p UInt16Slice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
+type Instance struct {
+	Image        string           `json:"image"`
+	Name         string           `json:"name"`
+	Hostname     string           `json:"hostname"`
+	IP           string           `json:"ip"`
+	IsManager    *bool            `json:"is_manager"`
+	Mem          string           `json:"mem"`
+	Cpu          string           `json:"cpu"`
+	Alias        string           `json:"alias"`
+	ServerCert   []byte           `json:"server_cert"`
+	ServerKey    []byte           `json:"server_key"`
+	CACert       []byte           `json:"ca_cert"`
+	Cert         []byte           `json:"cert"`
+	Key          []byte           `json:"key"`
+	IsDockerHost bool             `json:"is_docker_host"`
+	Docker       docker.DockerApi `json:"-"`
+	Session      *Session         `json:"-"`
+	Terminal     net.Conn         `json:"-"`
+	ctx          context.Context  `json:"-"`
+	tempPorts    []uint16         `json:"-"`
+	Ports        UInt16Slice
+	rw           sync.Mutex
+}
+
+func (i *Instance) SetUsedPort(port uint16) {
+	i.rw.Lock()
+	defer i.rw.Unlock()
+
+	for _, p := range i.tempPorts {
+		if p == port {
+			return
+		}
+	}
+	i.tempPorts = append(i.tempPorts, port)
+}
+func (i *Instance) GetUsedPorts() []uint16 {
+	i.rw.Lock()
+	defer i.rw.Unlock()
+
+	return i.tempPorts
+}
+func (i *Instance) CleanUsedPorts() {
+	i.rw.Lock()
+	defer i.rw.Unlock()
+
+	i.tempPorts = []uint16{}
+}
diff --git a/pwd/types/session.go b/pwd/types/session.go
new file mode 100644
index 0000000..1c0b384
--- /dev/null
+++ b/pwd/types/session.go
@@ -0,0 +1,55 @@
+package types
+
+import (
+	"sync"
+	"time"
+)
+
+type Session struct {
+	Id           string               `json:"id"`
+	Instances    map[string]*Instance `json:"instances"`
+	CreatedAt    time.Time            `json:"created_at"`
+	ExpiresAt    time.Time            `json:"expires_at"`
+	PwdIpAddress string               `json:"pwd_ip_address"`
+	Ready        bool                 `json:"ready"`
+	Stack        string               `json:"stack"`
+	StackName    string               `json:"stack_name"`
+	ImageName    string               `json:"image_name"`
+	Clients      []*Client            `json:"-"`
+	closingTimer *time.Timer          `json:"-"`
+	scheduled    bool                 `json:"-"`
+	ticker       *time.Ticker         `json:"-"`
+	rw           sync.Mutex           `json:"-"`
+	prepared     bool                 `json:"-"`
+}
+
+func (s *Session) Lock() {
+	s.rw.Lock()
+}
+
+func (s *Session) Unlock() {
+	s.rw.Unlock()
+}
+
+func (s *Session) StopTicker() {
+	if s.ticker != nil {
+		s.ticker.Stop()
+	}
+}
+func (s *Session) SetTicker(t *time.Ticker) {
+	s.ticker = t
+}
+func (s *Session) SetClosingTimer(t *time.Timer) {
+	s.closingTimer = t
+}
+func (s *Session) ClosingTimer() *time.Timer {
+	return s.closingTimer
+}
+
+func (s *Session) IsPrepared() bool {
+	return s.prepared
+}
+
+func (s *Session) SetPrepared() {
+	s.prepared = true
+}
diff --git a/storage/file.go b/storage/file.go
new file mode 100644
index 0000000..7b3dfa8
--- /dev/null
+++ b/storage/file.go
@@ -0,0 +1,150 @@
+package storage
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+	"sync"
+
+	"github.com/play-with-docker/play-with-docker/pwd/types"
+)
+
+type storage struct {
+	rw   sync.Mutex
+	path string
+	db   map[string]*types.Session
+}
+
+func (store *storage) SessionGet(sessionId string) (*types.Session, error) {
+	store.rw.Lock()
+	defer store.rw.Unlock()
+
+	s, found := store.db[sessionId]
+	if !found {
+		return nil, fmt.Errorf("%s", notFound)
+	}
+
+	return s, nil
+}
+func (store *storage) SessionPut(s *types.Session) error {
+	store.rw.Lock()
+	defer store.rw.Unlock()
+
+	store.db[s.Id] = s
+
+	return store.save()
+}
+
+func (store *storage) InstanceFindByIP(ip string) (*types.Instance, error) {
+	store.rw.Lock()
+	defer store.rw.Unlock()
+
+	for _, s := range store.db {
+		for _, i := range s.Instances {
+			if i.IP == ip {
+				return i, nil
+			}
+		}
+	}
+
+	return nil, fmt.Errorf("%s", notFound)
+}
+
+func (store *storage) InstanceFindByAlias(sessionPrefix, alias string) (*types.Instance, error) {
+	store.rw.Lock()
+	defer store.rw.Unlock()
+
+	for id, s := range store.db {
+		if strings.HasPrefix(id, sessionPrefix) {
+			for _, i := range s.Instances {
+				if i.Alias == alias {
+					return i, nil
+				}
+			}
+		}
+	}
+
+	return nil, fmt.Errorf("%s", notFound)
+}
+
+func (store *storage) SessionCount() (int, error) {
+	store.rw.Lock()
+	defer store.rw.Unlock()
+
+	return len(store.db), nil
+}
+
+func (store *storage) InstanceCount() (int, error) {
+	store.rw.Lock()
+	defer store.rw.Unlock()
+
+	var ins int
+
+	for _, s := range store.db {
+		ins += len(s.Instances)
+	}
+
+	return ins, nil
+}
+
+func (store *storage) ClientCount() (int, error) {
+	store.rw.Lock()
+	defer store.rw.Unlock()
+
+	var cli int
+
+	for _, s := range store.db {
+		cli += len(s.Clients)
+	}
+
+	return cli, nil
+}
+
+func (store *storage) SessionDelete(sessionId string) error {
+	store.rw.Lock()
+	defer store.rw.Unlock()
+
+	delete(store.db, sessionId)
+	return store.save()
+}
+
+func (store *storage) load() error {
+	file, err := os.Open(store.path)
+
+	if err == nil {
+		decoder := json.NewDecoder(file)
+		err = decoder.Decode(&store.db)
+
+		if err != nil {
+			return err
+		}
+	} else {
+		store.db = map[string]*types.Session{}
+	}
+
+	file.Close()
+	return nil
+}
+
+func (store *storage) save() error {
+	file, err := os.Create(store.path)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	encoder := json.NewEncoder(file)
+	err = encoder.Encode(&store.db)
+	return err
+}
+
+func NewFileStorage(path string) (StorageApi, error) {
+	s := &storage{path: path}
+
+	err := s.load()
+	if err != nil {
+		return nil, err
+	}
+
+	return s, nil
+}
diff --git a/storage/file_test.go b/storage/file_test.go
new file mode 100644
index 0000000..47fa848
--- /dev/null
+++ b/storage/file_test.go
@@ -0,0 +1,218 @@
+package storage
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"log"
+	"os"
+	"testing"
+
+	"github.com/play-with-docker/play-with-docker/pwd/types"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSessionPut(t *testing.T) {
+	tmpfile, err := ioutil.TempFile("", "pwd")
+	if err != nil {
+		log.Fatal(err)
+	}
+	tmpfile.Close()
+	os.Remove(tmpfile.Name())
+	defer os.Remove(tmpfile.Name())
+
+	storage, err := NewFileStorage(tmpfile.Name())
+
+	assert.Nil(t, err)
+
+	s := &types.Session{Id: "a session"}
+	err = storage.SessionPut(s)
+
+	assert.Nil(t, err)
+
+	var loadedSessions map[string]*types.Session
+	expectedSessions := map[string]*types.Session{}
+	expectedSessions[s.Id] = s
+
+	file, err := os.Open(tmpfile.Name())
+
+	assert.Nil(t, err)
+	defer file.Close()
+
+	decoder := json.NewDecoder(file)
+	err = decoder.Decode(&loadedSessions)
+
+	assert.Nil(t, err)
+
+	assert.EqualValues(t, expectedSessions, loadedSessions)
+}
+
+func TestSessionGet(t *testing.T) {
+	expectedSession := &types.Session{Id: "session1"}
+	sessions := map[string]*types.Session{}
+	sessions[expectedSession.Id] = expectedSession
+
+	tmpfile, err := ioutil.TempFile("", "pwd")
+	if err != nil {
+		log.Fatal(err)
+	}
+	encoder := json.NewEncoder(tmpfile)
+	err = encoder.Encode(&sessions)
+	assert.Nil(t, err)
+	tmpfile.Close()
+	defer os.Remove(tmpfile.Name())
+
+	storage, err := NewFileStorage(tmpfile.Name())
+
+	assert.Nil(t, err)
+
+	_, err = storage.SessionGet("bad id")
+	assert.True(t, NotFound(err))
+
+	loadedSession, err := storage.SessionGet("session1")
+	assert.Nil(t, err)
+
+	assert.Equal(t, expectedSession, loadedSession)
+}
+
+func TestInstanceFindByIP(t *testing.T) {
+	tmpfile, err := ioutil.TempFile("", "pwd")
+	if err != nil {
+		log.Fatal(err)
+	}
+	tmpfile.Close()
+	os.Remove(tmpfile.Name())
+	defer os.Remove(tmpfile.Name())
+
+	storage, err := NewFileStorage(tmpfile.Name())
+
+	assert.Nil(t, err)
+
+	i1 := &types.Instance{Name: "i1", IP: "10.0.0.1"}
+	i2 := &types.Instance{Name: "i2", IP: "10.1.0.1"}
+	s1 := &types.Session{Id: "session1", Instances: map[string]*types.Instance{"i1": i1}}
+	s2 := &types.Session{Id: "session2", Instances: map[string]*types.Instance{"i2": i2}}
+	err = storage.SessionPut(s1)
+	assert.Nil(t, err)
+	err = storage.SessionPut(s2)
+	assert.Nil(t, err)
+
+	foundInstance, err := storage.InstanceFindByIP("10.0.0.1")
+	assert.Nil(t, err)
+	assert.Equal(t, i1, foundInstance)
+
+	foundInstance, err = storage.InstanceFindByIP("10.1.0.1")
+	assert.Nil(t, err)
+	assert.Equal(t, i2, foundInstance)
+
+	foundInstance, err = storage.InstanceFindByIP("192.168.0.1")
+	assert.True(t, NotFound(err))
+	assert.Nil(t, foundInstance)
+}
+
+func TestInstanceFindByAlias(t *testing.T) {
+	tmpfile, err := ioutil.TempFile("", "pwd")
+	if err != nil {
+		log.Fatal(err)
+	}
+	tmpfile.Close()
+	os.Remove(tmpfile.Name())
+	defer os.Remove(tmpfile.Name())
+
+	storage, err := NewFileStorage(tmpfile.Name())
+
+	assert.Nil(t, err)
+
+	i1 := &types.Instance{Name: "i1", Alias: "foo", IP: "10.0.0.1"}
+	i2 := &types.Instance{Name: "i2", Alias: "foo", IP: "10.1.0.1"}
+	s1 := &types.Session{Id: "session1", Instances: map[string]*types.Instance{"i1": i1}}
+	s2 := &types.Session{Id: "session2", Instances: map[string]*types.Instance{"i2": i2}}
+	err = storage.SessionPut(s1)
+	assert.Nil(t, err)
+	err = storage.SessionPut(s2)
+	assert.Nil(t, err)
+
+	foundInstance, err := storage.InstanceFindByAlias("session1", "foo")
+	assert.Nil(t, err)
+	assert.Equal(t, i1, foundInstance)
+
+	foundInstance, err = storage.InstanceFindByAlias("session2", "foo")
+	assert.Nil(t, err)
+	assert.Equal(t, i2, foundInstance)
+
+	foundInstance, err = storage.InstanceFindByAlias("session1", "bar")
+	assert.True(t, NotFound(err))
+	assert.Nil(t, foundInstance)
+
+	foundInstance, err = storage.InstanceFindByAlias("session3", "foo")
+	assert.True(t, NotFound(err))
+	assert.Nil(t, foundInstance)
+}
+
+func TestCounts(t *testing.T) {
+	tmpfile, err := ioutil.TempFile("", "pwd")
+	if err != nil {
+		log.Fatal(err)
+	}
+	tmpfile.Close()
+	os.Remove(tmpfile.Name())
+	defer os.Remove(tmpfile.Name())
+
+	storage, err := NewFileStorage(tmpfile.Name())
+
+	assert.Nil(t, err)
+
+	c1 := &types.Client{}
+	i1 := &types.Instance{Name: "i1", Alias: "foo", IP: "10.0.0.1"}
+	i2 := &types.Instance{Name: "i2", Alias: "foo", IP: "10.1.0.1"}
+	s1 := &types.Session{Id: "session1", Instances: map[string]*types.Instance{"i1": i1}}
+	s2 := &types.Session{Id: "session2", Instances: map[string]*types.Instance{"i2": i2}}
+	s3 := &types.Session{Id: "session3", Clients: []*types.Client{c1}}
+
+	err = storage.SessionPut(s1)
+	assert.Nil(t, err)
+	err = storage.SessionPut(s2)
+	assert.Nil(t, err)
+	err = storage.SessionPut(s3)
+	assert.Nil(t, err)
+
+	num, err := storage.SessionCount()
+	assert.Nil(t, err)
+	assert.Equal(t, 3, num)
+
+	num, err = storage.InstanceCount()
+	assert.Nil(t, err)
+	assert.Equal(t, 2, num)
+
+	num, err = storage.ClientCount()
+	assert.Nil(t, err)
+	assert.Equal(t, 1, num)
+}
+
+func TestSessionDelete(t *testing.T) {
+	tmpfile, err := ioutil.TempFile("", "pwd")
+	if err != nil {
+		log.Fatal(err)
+	}
+	tmpfile.Close()
+	os.Remove(tmpfile.Name())
+	defer os.Remove(tmpfile.Name())
+
+	storage, err := NewFileStorage(tmpfile.Name())
+
+	assert.Nil(t, err)
+
+	s1 := &types.Session{Id: "session1"}
+	err = storage.SessionPut(s1)
+	assert.Nil(t, err)
+
+	found, err := storage.SessionGet(s1.Id)
+	assert.Nil(t, err)
+	assert.Equal(t, s1, found)
+
+	err = storage.SessionDelete(s1.Id)
+	assert.Nil(t, err)
+
+	found, err = storage.SessionGet(s1.Id)
+	assert.True(t, NotFound(err))
+	assert.Nil(t, found)
+}
diff --git a/storage/storage.go b/storage/storage.go
new file mode 100644
index 0000000..2cd7e96
--- /dev/null
+++ b/storage/storage.go
@@ -0,0 +1,23 @@
+package storage
+
+import "github.com/play-with-docker/play-with-docker/pwd/types"
+
+const notFound = "NotFound"
+
+func NotFound(e error) bool {
+	return e.Error() == notFound
+}
+
+type StorageApi interface {
+	SessionGet(sessionId string) (*types.Session, error)
+	SessionPut(*types.Session) error
+	SessionCount() (int, error)
+	SessionDelete(sessionId string) error
+
+	InstanceFindByAlias(sessionPrefix, alias string) (*types.Instance, error)
+	// Should have the session id too, soon
+	InstanceFindByIP(ip string) (*types.Instance, error)
+	InstanceCount() (int, error)
+
+	ClientCount() (int, error)
+}