diff --git a/weed/filer2/reader_at.go b/weed/filer2/reader_at.go
index b036e64fe..09d99dfb8 100644
--- a/weed/filer2/reader_at.go
+++ b/weed/filer2/reader_at.go
@@ -101,7 +101,7 @@ func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
 			return
 		}
 		bufferOffset := chunkStart - chunk.LogicOffset + chunk.Offset
-		copied := copy(p[chunkStart-startOffset:chunkStop-startOffset], buffer[bufferOffset:bufferOffset+chunkStop-chunkStart])
+		copied := copy(p[startOffset-offset:chunkStop-chunkStart+startOffset-offset], buffer[bufferOffset:bufferOffset+chunkStop-chunkStart])
 		n += copied
 		startOffset, remaining = startOffset+int64(copied), remaining-int64(copied)
 	}
@@ -111,6 +111,9 @@ func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
 	if remaining > 0 {
 		glog.V(4).Infof("zero2 [%d,%d)", n, n+int(remaining))
 		n += int(remaining)
+		if n > int(c.fileSize - offset){
+			n = int(c.fileSize - offset)
+		}
 	}
 
 	if offset+int64(n) >= c.fileSize {
diff --git a/weed/filer2/reader_at_test.go b/weed/filer2/reader_at_test.go
new file mode 100644
index 000000000..2a42cfd49
--- /dev/null
+++ b/weed/filer2/reader_at_test.go
@@ -0,0 +1,122 @@
+package filer2
+
+import (
+	"fmt"
+	"io"
+	"math"
+	"strconv"
+	"sync"
+	"testing"
+)
+
+type mockChunkCache struct {
+}
+
+func (m *mockChunkCache) GetChunk(fileId string, minSize uint64) (data []byte) {
+	x, _ := strconv.Atoi(fileId)
+	data = make([]byte, minSize)
+	for i := 0; i < int(minSize); i++ {
+		data[i] = byte(x)
+	}
+	return data
+}
+func (m *mockChunkCache) SetChunk(fileId string, data []byte) {
+}
+
+func TestReaderAt(t *testing.T) {
+
+	visibles := []VisibleInterval{
+		{
+			start:  1,
+			stop:   2,
+			fileId: "1",
+			chunkSize: 9,
+		},
+		{
+			start:  3,
+			stop:   4,
+			fileId: "3",
+			chunkSize: 1,
+		},
+		{
+			start:  5,
+			stop:   6,
+			fileId: "5",
+			chunkSize: 2,
+		},
+		{
+			start:  7,
+			stop:   9,
+			fileId: "7",
+			chunkSize: 2,
+		},
+		{
+			start:  9,
+			stop:   10,
+			fileId: "9",
+			chunkSize: 2,
+		},
+	}
+
+	readerAt := &ChunkReadAt{
+		chunkViews:   ViewFromVisibleIntervals(visibles, 0, math.MaxInt64),
+		lookupFileId: nil,
+		readerLock:   sync.Mutex{},
+		fileSize:     10,
+		chunkCache:   &mockChunkCache{},
+	}
+
+	testReadAt(t, readerAt, 0, 10, 10, io.EOF)
+	testReadAt(t, readerAt, 0, 12, 10, io.EOF)
+	testReadAt(t, readerAt, 2, 8, 8, io.EOF)
+	testReadAt(t, readerAt, 3, 6, 6, nil)
+
+}
+
+func testReadAt(t *testing.T, readerAt *ChunkReadAt, offset int64, size int, expected int, expectedErr error) {
+	data := make([]byte, size)
+	n, err := readerAt.ReadAt(data, offset)
+
+	if expected != n {
+		t.Errorf("unexpected read size: %d, expect: %d", n, expected)
+	}
+	if err != expectedErr {
+		t.Errorf("unexpected read error: %v, expect: %v", err, expectedErr)
+	}
+
+	for _, d := range data {
+		fmt.Printf("%x", d)
+	}
+	fmt.Println()
+}
+
+func TestReaderAt0(t *testing.T) {
+
+	visibles := []VisibleInterval{
+		{
+			start:  2,
+			stop:   5,
+			fileId: "1",
+			chunkSize: 9,
+		},
+		{
+			start:  7,
+			stop:   9,
+			fileId: "2",
+			chunkSize: 9,
+		},
+	}
+
+	readerAt := &ChunkReadAt{
+		chunkViews:   ViewFromVisibleIntervals(visibles, 0, math.MaxInt64),
+		lookupFileId: nil,
+		readerLock:   sync.Mutex{},
+		fileSize:     10,
+		chunkCache:   &mockChunkCache{},
+	}
+
+	testReadAt(t, readerAt, 0, 10, 10, io.EOF)
+	testReadAt(t, readerAt, 3, 16, 7, io.EOF)
+	testReadAt(t, readerAt, 3, 5, 5, nil)
+
+}