diff --git a/weed/storage/backend/memory_map/memory_map_backend.go b/weed/storage/backend/memory_map/memory_map_backend.go
index 44ef4d3e1..7fc2b4920 100644
--- a/weed/storage/backend/memory_map/memory_map_backend.go
+++ b/weed/storage/backend/memory_map/memory_map_backend.go
@@ -3,12 +3,10 @@ package memory_map
 import (
 	"os"
 	"time"
-
-	"github.com/chrislusf/seaweedfs/weed/storage/backend"
 )
 
 var (
-	_ backend.BackendStorageFile = &MemoryMappedFile{}
+	// _ backend.BackendStorageFile = &MemoryMappedFile{} // remove this to break import cycle
 )
 
 type MemoryMappedFile struct {
diff --git a/weed/storage/volume_create.go b/weed/storage/backend/volume_create.go
similarity index 68%
rename from weed/storage/volume_create.go
rename to weed/storage/backend/volume_create.go
index 422537a24..abb1f7238 100644
--- a/weed/storage/volume_create.go
+++ b/weed/storage/backend/volume_create.go
@@ -1,15 +1,14 @@
 // +build !linux,!windows
 
-package storage
+package backend
 
 import (
 	"os"
 
 	"github.com/chrislusf/seaweedfs/weed/glog"
-	"github.com/chrislusf/seaweedfs/weed/storage/backend"
 )
 
-func CreateVolumeFile(fileName string, preallocate int64, memoryMapSizeMB uint32) (backend.BackendStorageFile, error) {
+func CreateVolumeFile(fileName string, preallocate int64, memoryMapSizeMB uint32) (BackendStorageFile, error) {
 	file, e := os.OpenFile(fileName, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
 	if e != nil {
 		return nil, e
@@ -17,5 +16,5 @@ func CreateVolumeFile(fileName string, preallocate int64, memoryMapSizeMB uint32
 	if preallocate > 0 {
 		glog.V(0).Infof("Preallocated disk space for %s is not supported", fileName)
 	}
-	return backend.NewDiskFile(file), nil
+	return NewDiskFile(file), nil
 }
diff --git a/weed/storage/volume_create_linux.go b/weed/storage/backend/volume_create_linux.go
similarity index 72%
rename from weed/storage/volume_create_linux.go
rename to weed/storage/backend/volume_create_linux.go
index a854c531a..4602831ca 100644
--- a/weed/storage/volume_create_linux.go
+++ b/weed/storage/backend/volume_create_linux.go
@@ -1,16 +1,15 @@
 // +build linux
 
-package storage
+package backend
 
 import (
 	"os"
 	"syscall"
 
 	"github.com/chrislusf/seaweedfs/weed/glog"
-	"github.com/chrislusf/seaweedfs/weed/storage/backend"
 )
 
-func CreateVolumeFile(fileName string, preallocate int64, memoryMapSizeMB uint32) (backend.BackendStorageFile, error) {
+func CreateVolumeFile(fileName string, preallocate int64, memoryMapSizeMB uint32) (BackendStorageFile, error) {
 	file, e := os.OpenFile(fileName, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
 	if e != nil {
 		return nil, e
@@ -19,5 +18,5 @@ func CreateVolumeFile(fileName string, preallocate int64, memoryMapSizeMB uint32
 		syscall.Fallocate(int(file.Fd()), 1, 0, preallocate)
 		glog.V(0).Infof("Preallocated %d bytes disk space for %s", preallocate, fileName)
 	}
-	return backend.NewDiskFile(file), nil
+	return NewDiskFile(file), nil
 }
diff --git a/weed/storage/volume_create_windows.go b/weed/storage/backend/volume_create_windows.go
similarity index 82%
rename from weed/storage/volume_create_windows.go
rename to weed/storage/backend/volume_create_windows.go
index e347cbd1c..7d40ec0d7 100644
--- a/weed/storage/volume_create_windows.go
+++ b/weed/storage/backend/volume_create_windows.go
@@ -1,17 +1,16 @@
 // +build windows
 
-package storage
+package backend
 
 import (
 	"github.com/chrislusf/seaweedfs/weed/storage/backend/memory_map"
 	"golang.org/x/sys/windows"
 
 	"github.com/chrislusf/seaweedfs/weed/glog"
-	"github.com/chrislusf/seaweedfs/weed/storage/backend"
 	"github.com/chrislusf/seaweedfs/weed/storage/backend/memory_map/os_overloads"
 )
 
-func CreateVolumeFile(fileName string, preallocate int64, memoryMapSizeMB uint32) (backend.BackendStorageFile, error) {
+func CreateVolumeFile(fileName string, preallocate int64, memoryMapSizeMB uint32) (BackendStorageFile, error) {
 	if preallocate > 0 {
 		glog.V(0).Infof("Preallocated disk space for %s is not supported", fileName)
 	}
@@ -27,7 +26,7 @@ func CreateVolumeFile(fileName string, preallocate int64, memoryMapSizeMB uint32
 		if e != nil {
 			return nil, e
 		}
-		return backend.NewDiskFile(file), nil
+		return NewDiskFile(file), nil
 	}
 
 }
diff --git a/weed/storage/volume_loading.go b/weed/storage/volume_loading.go
index 64979cba1..b0b17af75 100644
--- a/weed/storage/volume_loading.go
+++ b/weed/storage/volume_loading.go
@@ -54,7 +54,7 @@ func (v *Volume) load(alsoLoadIndex bool, createDatIfMissing bool, needleMapKind
 		v.DataBackend = backend.NewDiskFile(dataFile)
 	} else {
 		if createDatIfMissing {
-			v.DataBackend, err = CreateVolumeFile(fileName+".dat", preallocate, v.MemoryMapMaxSizeMb)
+			v.DataBackend, err = backend.CreateVolumeFile(fileName+".dat", preallocate, v.MemoryMapMaxSizeMb)
 		} else {
 			return fmt.Errorf("Volume Data file %s.dat does not exist.", fileName)
 		}
diff --git a/weed/storage/volume_vacuum.go b/weed/storage/volume_vacuum.go
index ce3ab3a46..7518240d2 100644
--- a/weed/storage/volume_vacuum.go
+++ b/weed/storage/volume_vacuum.go
@@ -354,7 +354,7 @@ func (v *Volume) copyDataAndGenerateIndexFile(dstName, idxName string, prealloca
 	var (
 		dst backend.BackendStorageFile
 	)
-	if dst, err = CreateVolumeFile(dstName, preallocate, 0); err != nil {
+	if dst, err = backend.CreateVolumeFile(dstName, preallocate, 0); err != nil {
 		return
 	}
 	defer dst.Close()
@@ -383,7 +383,7 @@ func copyDataBasedOnIndexFile(srcDatName, srcIdxName, dstDatName, datIdxName str
 		srcDatBackend, dstDatBackend backend.BackendStorageFile
 		dataFile                     *os.File
 	)
-	if dstDatBackend, err = CreateVolumeFile(dstDatName, preallocate, 0); err != nil {
+	if dstDatBackend, err = backend.CreateVolumeFile(dstDatName, preallocate, 0); err != nil {
 		return
 	}
 	defer dstDatBackend.Close()