diff --git a/weed/filesys/wfs.go b/weed/filesys/wfs.go
index ef31a9258..37e9c105a 100644
--- a/weed/filesys/wfs.go
+++ b/weed/filesys/wfs.go
@@ -86,7 +86,7 @@ func NewSeaweedFileSystem(option *Option) *WFS {
 	cacheDir := path.Join(option.CacheDir, cacheUniqueId)
 	if option.CacheSizeMB > 0 {
 		os.MkdirAll(cacheDir, os.FileMode(0777)&^option.Umask)
-		wfs.chunkCache = chunk_cache.NewTieredChunkCache(256, cacheDir, option.CacheSizeMB)
+		wfs.chunkCache = chunk_cache.NewTieredChunkCache(256, cacheDir, option.CacheSizeMB, 1024*1024)
 	}
 
 	wfs.metaCache = meta_cache.NewMetaCache(path.Join(cacheDir, "meta"), option.UidGidMapper)
diff --git a/weed/server/webdav_server.go b/weed/server/webdav_server.go
index 121c0d2bb..f13e73a7b 100644
--- a/weed/server/webdav_server.go
+++ b/weed/server/webdav_server.go
@@ -100,7 +100,7 @@ type WebDavFile struct {
 
 func NewWebDavFileSystem(option *WebDavOption) (webdav.FileSystem, error) {
 
-	chunkCache := chunk_cache.NewTieredChunkCache(256, option.CacheDir, option.CacheSizeMB)
+	chunkCache := chunk_cache.NewTieredChunkCache(256, option.CacheDir, option.CacheSizeMB, 1024*1024)
 	return &WebDavFileSystem{
 		option:     option,
 		chunkCache: chunkCache,
diff --git a/weed/util/chunk_cache/chunk_cache.go b/weed/util/chunk_cache/chunk_cache.go
index 2b0c635a1..b4687d037 100644
--- a/weed/util/chunk_cache/chunk_cache.go
+++ b/weed/util/chunk_cache/chunk_cache.go
@@ -7,12 +7,6 @@ import (
 	"github.com/chrislusf/seaweedfs/weed/storage/needle"
 )
 
-const (
-	memCacheSizeLimit     = 1024 * 1024
-	onDiskCacheSizeLimit0 = memCacheSizeLimit
-	onDiskCacheSizeLimit1 = 4 * memCacheSizeLimit
-)
-
 type ChunkCache interface {
 	GetChunk(fileId string, minSize uint64) (data []byte)
 	SetChunk(fileId string, data []byte)
@@ -23,17 +17,21 @@ type TieredChunkCache struct {
 	memCache   *ChunkCacheInMemory
 	diskCaches []*OnDiskCacheLayer
 	sync.RWMutex
+	onDiskCacheSizeLimit0 uint64
+	onDiskCacheSizeLimit1 uint64
 }
 
-func NewTieredChunkCache(maxEntries int64, dir string, diskSizeMB int64) *TieredChunkCache {
+func NewTieredChunkCache(maxEntries int64, dir string, diskSizeInUnit int64, unitSize int64) *TieredChunkCache {
 
 	c := &TieredChunkCache{
 		memCache: NewChunkCacheInMemory(maxEntries),
 	}
 	c.diskCaches = make([]*OnDiskCacheLayer, 3)
-	c.diskCaches[0] = NewOnDiskCacheLayer(dir, "c0_1", diskSizeMB/4, 4)
-	c.diskCaches[1] = NewOnDiskCacheLayer(dir, "c1_4", diskSizeMB/4, 4)
-	c.diskCaches[2] = NewOnDiskCacheLayer(dir, "cache", diskSizeMB/2, 4)
+	c.onDiskCacheSizeLimit0 = uint64(unitSize)
+	c.onDiskCacheSizeLimit1 = 4 * c.onDiskCacheSizeLimit0
+	c.diskCaches[0] = NewOnDiskCacheLayer(dir, "c0_1", diskSizeInUnit*unitSize/4, 4)
+	c.diskCaches[1] = NewOnDiskCacheLayer(dir, "c1_4", diskSizeInUnit*unitSize/4, 4)
+	c.diskCaches[2] = NewOnDiskCacheLayer(dir, "cache", diskSizeInUnit*unitSize/2, 4)
 
 	return c
 }
@@ -51,7 +49,7 @@ func (c *TieredChunkCache) GetChunk(fileId string, minSize uint64) (data []byte)
 
 func (c *TieredChunkCache) doGetChunk(fileId string, minSize uint64) (data []byte) {
 
-	if minSize < memCacheSizeLimit {
+	if minSize < c.onDiskCacheSizeLimit0 {
 		data = c.memCache.GetChunk(fileId)
 		if len(data) >= int(minSize) {
 			return data
@@ -64,13 +62,13 @@ func (c *TieredChunkCache) doGetChunk(fileId string, minSize uint64) (data []byt
 		return nil
 	}
 
-	if minSize < onDiskCacheSizeLimit0 {
+	if minSize < c.onDiskCacheSizeLimit0 {
 		data = c.diskCaches[0].getChunk(fid.Key)
 		if len(data) >= int(minSize) {
 			return data
 		}
 	}
-	if minSize < onDiskCacheSizeLimit1 {
+	if minSize < c.onDiskCacheSizeLimit1 {
 		data = c.diskCaches[1].getChunk(fid.Key)
 		if len(data) >= int(minSize) {
 			return data
@@ -101,7 +99,7 @@ func (c *TieredChunkCache) SetChunk(fileId string, data []byte) {
 
 func (c *TieredChunkCache) doSetChunk(fileId string, data []byte) {
 
-	if len(data) < memCacheSizeLimit {
+	if len(data) < int(c.onDiskCacheSizeLimit0) {
 		c.memCache.SetChunk(fileId, data)
 	}
 
@@ -111,9 +109,9 @@ func (c *TieredChunkCache) doSetChunk(fileId string, data []byte) {
 		return
 	}
 
-	if len(data) < onDiskCacheSizeLimit0 {
+	if len(data) < int(c.onDiskCacheSizeLimit0) {
 		c.diskCaches[0].setChunk(fid.Key, data)
-	} else if len(data) < onDiskCacheSizeLimit1 {
+	} else if len(data) < int(c.onDiskCacheSizeLimit1) {
 		c.diskCaches[1].setChunk(fid.Key, data)
 	} else {
 		c.diskCaches[2].setChunk(fid.Key, data)
diff --git a/weed/util/chunk_cache/chunk_cache_on_disk_test.go b/weed/util/chunk_cache/chunk_cache_on_disk_test.go
index 558488f18..edcd23e62 100644
--- a/weed/util/chunk_cache/chunk_cache_on_disk_test.go
+++ b/weed/util/chunk_cache/chunk_cache_on_disk_test.go
@@ -14,9 +14,9 @@ func TestOnDisk(t *testing.T) {
 	tmpDir, _ := ioutil.TempDir("", "c")
 	defer os.RemoveAll(tmpDir)
 
-	totalDiskSizeMb := int64(32)
+	totalDiskSizeInKB := int64(32)
 
-	cache := NewTieredChunkCache(0, tmpDir, totalDiskSizeMb)
+	cache := NewTieredChunkCache(0, tmpDir, totalDiskSizeInKB, 1024)
 
 	writeCount := 5
 	type test_data struct {
@@ -26,7 +26,7 @@ func TestOnDisk(t *testing.T) {
 	}
 	testData := make([]*test_data, writeCount)
 	for i := 0; i < writeCount; i++ {
-		buff := make([]byte, 1024*1024)
+		buff := make([]byte, 1024)
 		rand.Read(buff)
 		testData[i] = &test_data{
 			data:   buff,
@@ -45,7 +45,7 @@ func TestOnDisk(t *testing.T) {
 
 	cache.Shutdown()
 
-	cache = NewTieredChunkCache(0, tmpDir, totalDiskSizeMb)
+	cache = NewTieredChunkCache(0, tmpDir, totalDiskSizeInKB, 1024)
 
 	for i := 0; i < writeCount; i++ {
 		data := cache.GetChunk(testData[i].fileId, testData[i].size)
diff --git a/weed/util/chunk_cache/on_disk_cache_layer.go b/weed/util/chunk_cache/on_disk_cache_layer.go
index c3192b548..a4d786510 100644
--- a/weed/util/chunk_cache/on_disk_cache_layer.go
+++ b/weed/util/chunk_cache/on_disk_cache_layer.go
@@ -14,11 +14,11 @@ type OnDiskCacheLayer struct {
 	diskCaches []*ChunkCacheVolume
 }
 
-func NewOnDiskCacheLayer(dir, namePrefix string, diskSizeMB int64, segmentCount int) *OnDiskCacheLayer {
+func NewOnDiskCacheLayer(dir, namePrefix string, diskSize int64, segmentCount int) *OnDiskCacheLayer {
 
-	volumeCount, volumeSize := int(diskSizeMB/30000), int64(30000)
+	volumeCount, volumeSize := int(diskSize/(30000*1024*1024)), int64(30000*1024*1024)
 	if volumeCount < segmentCount {
-		volumeCount, volumeSize = segmentCount, diskSizeMB/int64(segmentCount)
+		volumeCount, volumeSize = segmentCount, diskSize/int64(segmentCount)
 	}
 
 	c := &OnDiskCacheLayer{}