diff --git a/weed-fs/src/pkg/storage/compact_map.go b/weed-fs/src/pkg/storage/compact_map.go
new file mode 100644
index 000000000..4e83a76c8
--- /dev/null
+++ b/weed-fs/src/pkg/storage/compact_map.go
@@ -0,0 +1,158 @@
+package storage
+
+import ()
+
+type NeedleValue struct {
+	Key    Key
+	Offset uint32 "Volume offset" //since aligned to 8 bytes, range is 4G*8=32G
+	Size   uint32 "Size of the data portion"
+}
+
+const (
+	batch = 100000
+)
+
+type Key uint64
+
+type CompactSection struct {
+	values   []NeedleValue
+	overflow map[Key]*NeedleValue
+	start    Key
+	end      Key
+	counter  int
+}
+
+func NewCompactSection(start Key) CompactSection {
+	return CompactSection{
+		values:   make([]NeedleValue, batch),
+		overflow: make(map[Key]*NeedleValue),
+		start:    start,
+	}
+}
+func (cs *CompactSection) Set(key Key, offset uint32, size uint32) {
+	if key > cs.end {
+		cs.end = key
+	}
+	if i := cs.binarySearchValues(key); i >= 0 {
+		cs.values[i].Offset, cs.values[i].Size = offset, size
+	} else {
+	  needOverflow := cs.counter >= batch
+	  needOverflow = needOverflow || cs.counter > 0 && cs.values[cs.counter-1].Key > key
+		if needOverflow {
+			//println("start", cs.start, "counter", cs.counter, "key", key)
+			cs.overflow[key] = &NeedleValue{Key: key, Offset: offset, Size: size}
+		} else {
+			p := &cs.values[cs.counter]
+			p.Key, p.Offset, p.Size = key, offset, size
+			//println("added index", cs.counter, "key", key, cs.values[cs.counter].Key)
+			cs.counter++
+		}
+	}
+}
+func (cs *CompactSection) Delete(key Key) {
+	if i := cs.binarySearchValues(key); i >= 0 {
+		cs.values[i].Size = 0
+	}
+	delete(cs.overflow, key)
+}
+func (cs *CompactSection) Get(key Key) (*NeedleValue, bool) {
+	if v, ok := cs.overflow[key]; ok {
+		return v, true
+	}
+	if i := cs.binarySearchValues(key); i >= 0 {
+		return &cs.values[i], true
+	}
+	return nil, false
+}
+func (cs *CompactSection) binarySearchValues(key Key) int {
+	l, h := 0, cs.counter-1
+	if h >= 0 && cs.values[h].Key < key {
+		return -2
+	}
+	//println("looking for key", key)
+	for l <= h {
+		m := (l + h) / 2
+		//println("mid", m, "key", cs.values[m].Key, cs.values[m].Offset, cs.values[m].Size)
+		if cs.values[m].Key < key {
+			l = m + 1
+		} else if key < cs.values[m].Key {
+			h = m - 1
+		} else {
+			//println("found", m)
+			return m
+		}
+	}
+	return -1
+}
+
+//This map assumes mostly inserting increasing keys
+type CompactMap struct {
+	list []CompactSection
+}
+
+func NewCompactMap() CompactMap {
+	return CompactMap{}
+}
+
+func (cm *CompactMap) Set(key Key, offset uint32, size uint32) {
+	x := cm.binarySearchCompactSection(key)
+	if x < 0 {
+		//println(x, "creating", len(cm.list), "section1, starting", key)
+		cm.list = append(cm.list, NewCompactSection(key))
+		x = len(cm.list) - 1
+	}
+	cm.list[x].Set(key, offset, size)
+}
+func (cm *CompactMap) Delete(key Key) {
+	x := cm.binarySearchCompactSection(key)
+	if x < 0 {
+		return
+	}
+	cm.list[x].Delete(key)
+}
+func (cm *CompactMap) Get(key Key) (*NeedleValue, bool) {
+	x := cm.binarySearchCompactSection(key)
+	if x < 0 {
+		return nil, false
+	}
+	return cm.list[x].Get(key)
+}
+func (cm *CompactMap) binarySearchCompactSection(key Key) int {
+	l, h := 0, len(cm.list)-1
+	if h < 0 {
+		return -5
+	}
+	if cm.list[h].start <= key {
+		if cm.list[h].counter < batch || key <= cm.list[h].end{
+			return h
+		} else {
+			return -4
+		}
+	}
+	for l <= h {
+		m := (l + h) / 2
+		if key < cm.list[m].start {
+			h = m - 1
+		} else { // cm.list[m].start <= key
+			if cm.list[m+1].start <= key {
+				l = m + 1
+			} else {
+				return m
+			}
+		}
+	}
+	return -3
+}
+
+func (cm *CompactMap) Peek() {
+	for k, v := range cm.list[0].values {
+		if k < 100 {
+			println("[", v.Key, v.Offset, v.Size, "]")
+		}
+	}
+  for k, v := range cm.list[0].overflow {
+    if k < 100 {
+      println("o[", v.Key, v.Offset, v.Size, "]")
+    }
+  }
+}
diff --git a/weed-fs/src/pkg/storage/compact_map_perf_test.go b/weed-fs/src/pkg/storage/compact_map_perf_test.go
new file mode 100644
index 000000000..2e2227279
--- /dev/null
+++ b/weed-fs/src/pkg/storage/compact_map_perf_test.go
@@ -0,0 +1,43 @@
+package storage
+
+import (
+	"testing"
+  "log"
+  "os"
+  "pkg/util"
+)
+
+func TestMemoryUsage(t *testing.T) {
+
+  indexFile, ie := os.OpenFile("sample.idx", os.O_RDWR|os.O_RDONLY, 0644)
+  if ie != nil {
+    log.Fatalln(ie)
+  }
+  LoadNewNeedleMap(indexFile)
+    
+}
+
+func LoadNewNeedleMap(file *os.File) CompactMap {
+  m := NewCompactMap()
+  bytes := make([]byte, 16*1024)
+  count, e := file.Read(bytes)
+  if count > 0 {
+    fstat, _ := file.Stat()
+    log.Println("Loading index file", fstat.Name(), "size", fstat.Size())
+  }
+  for count > 0 && e == nil {
+    for i := 0; i < count; i += 16 {
+      key := util.BytesToUint64(bytes[i : i+8])
+      offset := util.BytesToUint32(bytes[i+8 : i+12])
+      size := util.BytesToUint32(bytes[i+12 : i+16])
+      if offset > 0 {
+        m.Set(Key(key), offset, size)
+      } else {
+        //delete(m, key)
+      }
+    }
+
+    count, e = file.Read(bytes)
+  }
+  return m
+}
diff --git a/weed-fs/src/pkg/storage/compact_map_test.go b/weed-fs/src/pkg/storage/compact_map_test.go
new file mode 100644
index 000000000..6c3bb6e96
--- /dev/null
+++ b/weed-fs/src/pkg/storage/compact_map_test.go
@@ -0,0 +1,65 @@
+package storage
+
+import (
+	"testing"
+)
+
+func TestXYZ(t *testing.T) {
+	m := NewCompactMap()
+	for i := uint32(0); i < 100*batch; i += 2 {
+		m.Set(Key(i), i, i)
+	}
+
+	for i := uint32(0); i < 100*batch; i += 37 {
+		m.Delete(Key(i))
+	}
+
+	for i := uint32(0); i < 10*batch; i += 3 {
+		m.Set(Key(i), i+11, i+5)
+	}
+
+//	for i := uint32(0); i < 100; i++ {
+//		if v := m.Get(Key(i)); v != nil {
+//			println(i, "=", v.Key, v.Offset, v.Size)
+//		}
+//	}
+	
+	for i := uint32(0); i < 10*batch; i++ {
+    v, ok := m.Get(Key(i))
+		if i%3 == 0 {
+      if !ok {
+        t.Fatal("key", i, "missing!")
+      }
+			if v.Size != i+5 {
+				t.Fatal("key", i, "size", v.Size)
+			}
+		} else if i%37 == 0 {
+      if ok && v.Size > 0 {
+				t.Fatal("key", i, "should have been deleted needle value", v)
+			}
+		} else if i%2 == 0 {
+	    if v.Size != i {
+				t.Fatal("key", i, "size", v.Size)
+			}
+		}
+	}
+
+  //println("cm.list =", len(m.list))
+
+	for i := uint32(10 * batch); i < 100*batch; i++ {
+    v, ok := m.Get(Key(i))
+		if i%37 == 0 {
+      if ok && v.Size > 0 {
+        t.Fatal("key", i, "should have been deleted needle value", v)
+      }
+		} else if i%2 == 0 {
+		  if v==nil{
+        t.Fatal("key", i, "missing")
+		  }
+			if v.Size != i {
+				t.Fatal("key", i, "size", v.Size)
+			}
+		}
+	}
+
+}
diff --git a/weed-fs/src/pkg/storage/needle_map.go b/weed-fs/src/pkg/storage/needle_map.go
index 4e6406d6a..53a640052 100644
--- a/weed-fs/src/pkg/storage/needle_map.go
+++ b/weed-fs/src/pkg/storage/needle_map.go
@@ -6,20 +6,15 @@ import (
 	"pkg/util"
 )
 
-type NeedleValue struct {
-	Offset uint32 "Volume offset" //since aligned to 8 bytes, range is 4G*8=32G
-	Size   uint32 "Size of the data portion"
-}
-
 type NeedleMap struct {
 	indexFile *os.File
-	m         map[uint64]NeedleValue //mapping needle key(uint64) to NeedleValue
+	m         CompactMap
 	bytes     []byte
 }
 
 func NewNeedleMap(file *os.File) *NeedleMap {
 	nm := &NeedleMap{
-		m:         make(map[uint64]NeedleValue),
+		m:         NewCompactMap(),
 		bytes:     make([]byte, 16),
 		indexFile: file,
 	}
@@ -43,31 +38,31 @@ func LoadNeedleMap(file *os.File) *NeedleMap {
 			key := util.BytesToUint64(bytes[i : i+8])
 			offset := util.BytesToUint32(bytes[i+8 : i+12])
 			size := util.BytesToUint32(bytes[i+12 : i+16])
-			if offset>0 {
-   			nm.m[key] = NeedleValue{util.Offset: offset, Size: size}
-   	  }else{
-        delete(nm.m, key)
-   	  }
-		}     
-		
+			if offset > 0 {
+				nm.m.Set(Key(key), offset, size)
+			} else {
+				nm.m.Delete(Key(key))
+			}
+		}
+
 		count, e = nm.indexFile.Read(bytes)
 	}
 	return nm
-}     
+}
 
 func (nm *NeedleMap) Put(key uint64, offset uint32, size uint32) (int, error) {
-	nm.m[key] = NeedleValue{Offset: offset, Size: size}
+	nm.m.Set(Key(key), offset, size)
 	util.Uint64toBytes(nm.bytes[0:8], key)
 	util.Uint32toBytes(nm.bytes[8:12], offset)
 	util.Uint32toBytes(nm.bytes[12:16], size)
 	return nm.indexFile.Write(nm.bytes)
 }
-func (nm *NeedleMap) Get(key uint64) (element NeedleValue, ok bool) {
-	element, ok = nm.m[key]
+func (nm *NeedleMap) Get(key uint64) (element *NeedleValue, ok bool) {
+	element, ok = nm.m.Get(Key(key))
 	return
 }
 func (nm *NeedleMap) Delete(key uint64) {
-	delete(nm.m, key)
+	nm.m.Delete(Key(key))
 	util.Uint64toBytes(nm.bytes[0:8], key)
 	util.Uint32toBytes(nm.bytes[8:12], 0)
 	util.Uint32toBytes(nm.bytes[12:16], 0)
@@ -76,6 +71,3 @@ func (nm *NeedleMap) Delete(key uint64) {
 func (nm *NeedleMap) Close() {
 	nm.indexFile.Close()
 }
-func (nm *NeedleMap) Length() int{
-  return len(nm.m)
-}
diff --git a/weed-fs/src/pkg/storage/sample.idx b/weed-fs/src/pkg/storage/sample.idx
new file mode 100644
index 000000000..44918b41d
Binary files /dev/null and b/weed-fs/src/pkg/storage/sample.idx differ