diff --git a/backend/interface.go b/backend/interface.go
index 24424dd96..9fff4bf1e 100644
--- a/backend/interface.go
+++ b/backend/interface.go
@@ -40,6 +40,9 @@ type Backend interface {
 	// and saves it in p. Load has the same semantics as io.ReaderAt.
 	Load(h Handle, p []byte, off int64) (int, error)
 
+	// Save stores the data in the backend under the given handle.
+	Save(h Handle, p []byte) error
+
 	// Stat returns information about the blob identified by h.
 	Stat(h Handle) (BlobInfo, error)
 }
diff --git a/backend/local/local.go b/backend/local/local.go
index 0d12e4109..4183ff474 100644
--- a/backend/local/local.go
+++ b/backend/local/local.go
@@ -225,6 +225,33 @@ func (b *Local) Load(h backend.Handle, p []byte, off int64) (n int, err error) {
 	return io.ReadFull(f, p)
 }
 
+// Save stores data in the backend at the handle.
+func (b *Local) Save(h backend.Handle, p []byte) (err error) {
+	if err := h.Valid(); err != nil {
+		return err
+	}
+
+	f, err := os.Create(filename(b.p, h.Type, h.Name))
+	if err != nil {
+		return err
+	}
+
+	n, err := f.Write(p)
+	if err != nil {
+		return err
+	}
+
+	if n != len(p) {
+		return errors.New("not all bytes writen")
+	}
+
+	if err = f.Sync(); err != nil {
+		return err
+	}
+
+	return f.Close()
+}
+
 // Stat returns information about a blob.
 func (b *Local) Stat(h backend.Handle) (backend.BlobInfo, error) {
 	if err := h.Valid(); err != nil {
diff --git a/backend/mem/mem_backend.go b/backend/mem/mem_backend.go
index b999efd1d..0de0c0837 100644
--- a/backend/mem/mem_backend.go
+++ b/backend/mem/mem_backend.go
@@ -130,13 +130,13 @@ func memCreate(be *MemoryBackend) (backend.Blob, error) {
 }
 
 func memLoad(be *MemoryBackend, h backend.Handle, p []byte, off int64) (int, error) {
-	be.m.Lock()
-	defer be.m.Unlock()
-
 	if err := h.Valid(); err != nil {
 		return 0, err
 	}
 
+	be.m.Lock()
+	defer be.m.Unlock()
+
 	if h.Type == backend.Config {
 		h.Name = ""
 	}
@@ -163,6 +163,26 @@ func memLoad(be *MemoryBackend, h backend.Handle, p []byte, off int64) (int, err
 	return n, nil
 }
 
+func memSave(be *MemoryBackend, h backend.Handle, p []byte) error {
+	if err := h.Valid(); err != nil {
+		return err
+	}
+
+	be.m.Lock()
+	defer be.m.Unlock()
+
+	if h.Type == backend.Config {
+		h.Name = ""
+	}
+
+	debug.Log("MemoryBackend.Save", "save %v bytes at %v", len(p), h)
+	buf := make([]byte, len(p))
+	copy(buf, p)
+	be.data[entry{h.Type, h.Name}] = buf
+
+	return nil
+}
+
 func memStat(be *MemoryBackend, h backend.Handle) (backend.BlobInfo, error) {
 	be.m.Lock()
 	defer be.m.Unlock()
diff --git a/backend/mock_backend.go b/backend/mock_backend.go
index 1075292d6..9e692883f 100644
--- a/backend/mock_backend.go
+++ b/backend/mock_backend.go
@@ -8,6 +8,7 @@ type MockBackend struct {
 	CloseFn    func() error
 	CreateFn   func() (Blob, error)
 	LoadFn     func(h Handle, p []byte, off int64) (int, error)
+	SaveFn     func(h Handle, p []byte) error
 	StatFn     func(h Handle) (BlobInfo, error)
 	ListFn     func(Type, <-chan struct{}) <-chan string
 	RemoveFn   func(Type, string) error
@@ -48,6 +49,14 @@ func (m *MockBackend) Load(h Handle, p []byte, off int64) (int, error) {
 	return m.LoadFn(h, p, off)
 }
 
+func (m *MockBackend) Save(h Handle, p []byte) error {
+	if m.SaveFn == nil {
+		return errors.New("not implemented")
+	}
+
+	return m.SaveFn(h, p)
+}
+
 func (m *MockBackend) Stat(h Handle) (BlobInfo, error) {
 	if m.StatFn == nil {
 		return BlobInfo{}, errors.New("not implemented")
diff --git a/backend/s3/s3.go b/backend/s3/s3.go
index a46cdb22d..9fd5c6152 100644
--- a/backend/s3/s3.go
+++ b/backend/s3/s3.go
@@ -163,9 +163,36 @@ func (be S3Backend) Load(h backend.Handle, p []byte, off int64) (int, error) {
 		}
 	}
 
+	<-be.connChan
+	defer func() {
+		be.connChan <- struct{}{}
+	}()
 	return io.ReadFull(obj, p)
 }
 
+// Save stores data in the backend at the handle.
+func (be S3Backend) Save(h backend.Handle, p []byte) (err error) {
+	if err := h.Valid(); err != nil {
+		return err
+	}
+
+	debug.Log("s3.Save", "%v bytes at %d", len(p), h)
+
+	path := s3path(h.Type, h.Name)
+
+	<-be.connChan
+	defer func() {
+		be.connChan <- struct{}{}
+	}()
+
+	debug.Log("s3.Save", "PutObject(%v, %v, %v, %v)",
+		be.bucketname, path, int64(len(p)), "binary/octet-stream")
+	n, err := be.client.PutObject(be.bucketname, path, bytes.NewReader(p), "binary/octet-stream")
+	debug.Log("s3.Save", "%v -> %v bytes, err %#v", path, n, err)
+
+	return err
+}
+
 // Stat returns information about a blob.
 func (be S3Backend) Stat(h backend.Handle) (backend.BlobInfo, error) {
 	debug.Log("s3.Stat", "%v")
diff --git a/backend/sftp/sftp.go b/backend/sftp/sftp.go
index e40a3cd00..c5017bdfc 100644
--- a/backend/sftp/sftp.go
+++ b/backend/sftp/sftp.go
@@ -373,6 +373,29 @@ func (r *SFTP) Load(h backend.Handle, p []byte, off int64) (n int, err error) {
 	return io.ReadFull(f, p)
 }
 
+// Save stores data in the backend at the handle.
+func (r *SFTP) Save(h backend.Handle, p []byte) (err error) {
+	if err := h.Valid(); err != nil {
+		return err
+	}
+
+	f, err := r.c.Create(r.filename(h.Type, h.Name))
+	if err != nil {
+		return err
+	}
+
+	n, err := f.Write(p)
+	if err != nil {
+		return err
+	}
+
+	if n != len(p) {
+		return errors.New("not all bytes writen")
+	}
+
+	return f.Close()
+}
+
 // Stat returns information about a blob.
 func (r *SFTP) Stat(h backend.Handle) (backend.BlobInfo, error) {
 	if err := h.Valid(); err != nil {