diff --git a/commands/root.go b/commands/root.go
index 9342d3a..1db52cd 100644
--- a/commands/root.go
+++ b/commands/root.go
@@ -4,12 +4,14 @@ import (
 	"fmt"
 	"net/http"
 	"os"
+	"strconv"
+	"os/user"
 
 	"golang.org/x/net/context"
 	"golang.org/x/oauth2/google"
 
 	"google.golang.org/api/compute/v1"
-	"google.golang.org/cloud/compute/metadata"
+	"cloud.google.com/go/compute/metadata"
 
 	"gopkg.in/inconshreveable/log15.v2"
 
@@ -169,7 +171,9 @@ func (c *RootCommand) runVolumePlugin() error {
 	}
 
 	h := volume.NewHandler(d)
-	if err := h.ServeUnix("docker", "gce"); err != nil {
+	u, _ := user.Lookup("root")
+	gid, _ := strconv.Atoi(u.Gid)
+	if err := h.ServeUnix("gce", gid); err != nil {
 		return fmt.Errorf("error starting volume driver server: %s", err)
 	}
 
diff --git a/plugin/volume.go b/plugin/volume.go
index 31f2688..8b4606c 100644
--- a/plugin/volume.go
+++ b/plugin/volume.go
@@ -16,9 +16,10 @@ import (
 var WaitStatusTimeout = 100 * time.Second
 
 type Volume struct {
-	Root string
-	p    providers.DiskProvider
-	fs   Filesystem
+	Root   string
+	p      providers.DiskProvider
+	fs     Filesystem
+	mounts map[string][]string
 }
 
 func NewVolume(c *http.Client, project, zone, instance string) (*Volume, error) {
@@ -31,33 +32,34 @@ func NewVolume(c *http.Client, project, zone, instance string) (*Volume, error)
 		Root: "/mnt/",
 		p:    p,
 		fs:   NewFilesystem(),
+		mounts: map[string][]string{},
 	}, nil
 }
 
-func (v *Volume) Create(r volume.Request) volume.Response {
+func (v *Volume) Create(r *volume.CreateRequest) error {
 	log15.Debug("create request received", "name", r.Name)
 	start := time.Now()
-	config, err := v.createDiskConfig(r)
+	config, err := v.createDiskConfig(r.Name, r)
 	if err != nil {
-		return buildReponseError(err)
+		return err
 	}
 
 	if err := v.p.Create(config); err != nil {
-		return buildReponseError(err)
+		return err
 	}
 
 	log15.Info("disk created", "disk", r.Name, "elapsed", time.Since(start))
-	return volume.Response{}
+	return nil
 }
 
-func (v *Volume) List(volume.Request) volume.Response {
+func (v *Volume) List() (*volume.ListResponse, error) {
 	log15.Debug("list request received")
 	disks, err := v.p.List()
 	if err != nil {
-		return buildReponseError(err)
+		return nil, err
 	}
 
-	r := volume.Response{}
+	r := volume.ListResponse{}
 	for _, d := range disks {
 		if d.Status != "READY" {
 			continue
@@ -68,32 +70,32 @@ func (v *Volume) List(volume.Request) volume.Response {
 		})
 	}
 
-	return r
+	return &r, nil
 }
 
-func (v *Volume) Capabilities(volume.Request) volume.Response {
+func (v *Volume) Capabilities() *volume.CapabilitiesResponse {
 	log15.Debug("capabilities request received")
-	return volume.Response{
+	return &volume.CapabilitiesResponse{
 		Capabilities: volume.Capability{Scope: "local"},
 	}
 }
 
-func (v *Volume) Get(r volume.Request) volume.Response {
+func (v *Volume) Get(r *volume.GetRequest) (*volume.GetResponse, error) {
 	log15.Debug("get request received")
 	disks, err := v.p.List()
 	if err != nil {
-		return buildReponseError(err)
+		return nil, err
 	}
 
-	resp := volume.Response{}
+	resp := volume.GetResponse{}
 	for _, d := range disks {
 		if d.Name != r.Name {
 			continue
 		}
 
-		config, err := v.createDiskConfig(r)
+		config, err := v.createDiskConfig(r.Name, nil)
 		if err != nil {
-			return buildReponseError(err)
+			return nil, err
 		}
 
 		resp.Volume = &volume.Volume{
@@ -102,71 +104,79 @@ func (v *Volume) Get(r volume.Request) volume.Response {
 		}
 	}
 
-	return resp
+	return &resp, nil
 }
 
-func (v *Volume) Remove(r volume.Request) volume.Response {
+func (v *Volume) Remove(r *volume.RemoveRequest) error {
 	log15.Debug("remove request received", "name", r.Name)
 	start := time.Now()
 
-	config, err := v.createDiskConfig(r)
+	config, err := v.createDiskConfig(r.Name, nil)
 	if err != nil {
-		return buildReponseError(err)
+		return err
 	}
 
 	if err := v.p.Delete(config); err != nil {
-		return buildReponseError(err)
+		return err
 	}
 
 	log15.Info("disk removed", "disk", r.Name, "elapsed", time.Since(start))
-	return volume.Response{}
+	return nil
 }
 
-func (v *Volume) Path(r volume.Request) volume.Response {
-	config, err := v.createDiskConfig(r)
+func (v *Volume) Path(r *volume.PathRequest) (*volume.PathResponse, error) {
+	config, err := v.createDiskConfig(r.Name, nil)
 	if err != nil {
-		return buildReponseError(err)
+		return nil, err
 	}
 
 	mnt := config.MountPoint(v.Root)
 	log15.Debug("path request received", "name", r.Name, "mnt", mnt)
 
 	if err := v.createMountPoint(config); err != nil {
-		return buildReponseError(err)
+		return nil, err
 	}
 
-	return volume.Response{Mountpoint: mnt}
+	return &volume.PathResponse{Mountpoint: mnt}, nil
 }
 
-func (v *Volume) Mount(r volume.Request) volume.Response {
+func (v *Volume) Mount(r *volume.MountRequest) (*volume.MountResponse, error) {
 	log15.Debug("mount request received", "name", r.Name)
 	start := time.Now()
-
-	config, err := v.createDiskConfig(r)
+	config, err := v.createDiskConfig(r.Name, nil)
 	if err != nil {
-		return buildReponseError(err)
+		return nil, err
 	}
 
-	if err := v.createMountPoint(config); err != nil {
-		return buildReponseError(err)
-	}
+	if v.trackMount(r.ID, r.Name) {
+		if err := v.createMountPoint(config); err != nil {
+			v.resetMount(r.Name)
+			return nil, err
+		}
 
-	if err := v.p.Attach(config); err != nil {
-		return buildReponseError(err)
-	}
+		if err := v.p.Attach(config); err != nil {
+			v.resetMount(r.Name)
+			return nil, err
+		}
 
-	if err := v.fs.Format(config.Dev()); err != nil {
-		return buildReponseError(err)
-	}
+		if err := v.fs.Format(config.Dev()); err != nil {
+			v.resetMount(r.Name)
+			return nil, err
+		}
 
-	if err := v.fs.Mount(config.Dev(), config.MountPoint(v.Root)); err != nil {
-		return buildReponseError(err)
+		if err := v.fs.Mount(config.Dev(), config.MountPoint(v.Root)); err != nil {
+			v.resetMount(r.Name)
+			return nil, err
+		}
+
+		log15.Info("disk mounted", "disk", r.Name, "elapsed", time.Since(start))
+	} else {
+		log15.Info("disk already mounted", "disk", r.Name, "elapsed", time.Since(start))
 	}
 
-	log15.Info("disk mounted", "disk", r.Name, "elapsed", time.Since(start))
-	return volume.Response{
+	return &volume.MountResponse{
 		Mountpoint: config.MountPoint(v.Root),
-	}
+	}, nil
 }
 
 func (v *Volume) createMountPoint(c *providers.DiskConfig) error {
@@ -187,54 +197,91 @@ func (v *Volume) createMountPoint(c *providers.DiskConfig) error {
 	return nil
 }
 
-func (v *Volume) Unmount(r volume.Request) volume.Response {
+func (v *Volume) Unmount(r *volume.UnmountRequest) error {
 	log15.Debug("unmount request received", "name", r.Name)
 	start := time.Now()
-	config, err := v.createDiskConfig(r)
+	config, err := v.createDiskConfig(r.Name, nil)
 	if err != nil {
-		return buildReponseError(err)
+		return err
 	}
 
-	if err := v.fs.Unmount(config.MountPoint(v.Root)); err != nil {
-		return buildReponseError(err)
-	}
+	if v.trackUnmount(r.ID, r.Name) {
+		if err := v.fs.Unmount(config.MountPoint(v.Root)); err != nil {
+			return err
+		}
+
+		if err := v.p.Detach(config); err != nil {
+			return err
+		}
 
-	if err := v.p.Detach(config); err != nil {
-		return buildReponseError(err)
+		log15.Info("disk unmounted", "disk", r.Name, "elapsed", time.Since(start))
+	} else {
+		log15.Info("other mounts active, not unmounting", "disk", r.Name, "elapsed", time.Since(start))
 	}
 
-	log15.Info("disk unmounted", "disk", r.Name, "elapsed", time.Since(start))
-	return volume.Response{}
+	return nil
 }
 
-func (v *Volume) createDiskConfig(r volume.Request) (*providers.DiskConfig, error) {
-	config := &providers.DiskConfig{Name: r.Name}
-
-	for key, value := range r.Options {
-		switch key {
-		case "Name":
-			config.Name = value
-		case "Type":
-			config.Type = value
-		case "SizeGb":
-			var err error
-			config.SizeGb, err = strconv.ParseInt(value, 10, 64)
-			if err != nil {
-				return nil, err
+func (v *Volume) createDiskConfig(name string, r *volume.CreateRequest) (*providers.DiskConfig, error) {
+	config := &providers.DiskConfig{Name: name}
+
+	if r != nil {
+		for key, value := range r.Options {
+			switch key {
+			case "Name":
+				config.Name = value
+			case "Type":
+				config.Type = value
+			case "SizeGb":
+				var err error
+				config.SizeGb, err = strconv.ParseInt(value, 10, 64)
+				if err != nil {
+					return nil, err
+				}
+			case "SourceSnapshot":
+				config.SourceSnapshot = value
+			case "SourceImage":
+				config.SourceImage = value
+			default:
+				return nil, fmt.Errorf("unknown option %q", key)
 			}
-		case "SourceSnapshot":
-			config.SourceSnapshot = value
-		case "SourceImage":
-			config.SourceImage = value
-		default:
-			return nil, fmt.Errorf("unknown option %q", key)
 		}
 	}
 
 	return config, config.Validate()
 }
 
-func buildReponseError(err error) volume.Response {
-	log15.Error("request failed", "error", err.Error())
-	return volume.Response{Err: err.Error()}
+// Return if mount action needed
+func (v *Volume) trackMount(id string, name string) bool {
+	existing, ok := v.mounts[name]
+	if !ok || len(existing) == 0 {
+		v.mounts[name] = []string{id}
+		return true
+	} else {
+		v.mounts[name] = append(existing, id)
+		return false
+	}
+}
+
+// Return if unmount action needed
+func (v *Volume) trackUnmount(id string, name string) bool {
+	existing, ok := v.mounts[name]
+	if !ok {
+		// In case service restarted and state has been lost, most likely unmount means unmount
+		return true
+	}
+
+	for i, oldId := range existing {
+		if oldId == id {
+			v.mounts[name] = append(v.mounts[name][:i], v.mounts[name][i+1:]...)
+			return len(v.mounts[name]) == 0
+		}
+	}
+
+	return false
+}
+
+// Reset tracked mount in case of errors such as disks already being attached
+func (v *Volume) resetMount(name string) {
+	delete(v.mounts, name)
 }