diff --git a/weed/filer/reader_cache.go b/weed/filer/reader_cache.go
index c319f6c78..4c92f71c8 100644
--- a/weed/filer/reader_cache.go
+++ b/weed/filer/reader_cache.go
@@ -18,7 +18,7 @@ type ReaderCache struct {
 }
 
 type SingleChunkCacher struct {
-	sync.RWMutex
+	sync.Mutex
 	cond          *sync.Cond
 	parent        *ReaderCache
 	chunkFileId   string
@@ -183,8 +183,8 @@ func (s *SingleChunkCacher) destroy() {
 }
 
 func (s *SingleChunkCacher) readChunkAt(buf []byte, offset int64) (int, error) {
-	s.RLock()
-	defer s.RUnlock()
+	s.Lock()
+	defer s.Unlock()
 
 	for s.completedTime.IsZero() {
 		s.cond.Wait()
diff --git a/weed/filer/reader_pattern.go b/weed/filer/reader_pattern.go
index b860bc577..ec73c59a2 100644
--- a/weed/filer/reader_pattern.go
+++ b/weed/filer/reader_pattern.go
@@ -1,8 +1,8 @@
 package filer
 
 type ReaderPattern struct {
-	isStreaming    bool
-	lastReadOffset int64
+	isSequentialCounter int64
+	lastReadStopOffset  int64
 }
 
 // For streaming read: only cache the first chunk
@@ -10,29 +10,20 @@ type ReaderPattern struct {
 
 func NewReaderPattern() *ReaderPattern {
 	return &ReaderPattern{
-		isStreaming:    true,
-		lastReadOffset: -1,
+		isSequentialCounter: 0,
+		lastReadStopOffset:  0,
 	}
 }
 
 func (rp *ReaderPattern) MonitorReadAt(offset int64, size int) {
-	isStreaming := true
-	if rp.lastReadOffset > offset {
-		isStreaming = false
+	if rp.lastReadStopOffset == offset {
+		rp.isSequentialCounter++
+	} else {
+		rp.isSequentialCounter--
 	}
-	if rp.lastReadOffset == -1 {
-		if offset != 0 {
-			isStreaming = false
-		}
-	}
-	rp.lastReadOffset = offset
-	rp.isStreaming = isStreaming
-}
-
-func (rp *ReaderPattern) IsStreamingMode() bool {
-	return rp.isStreaming
+	rp.lastReadStopOffset = offset + int64(size)
 }
 
 func (rp *ReaderPattern) IsRandomMode() bool {
-	return !rp.isStreaming
+	return rp.isSequentialCounter >= 0
 }
diff --git a/weed/mount/page_writer.go b/weed/mount/page_writer.go
index 016c4841a..7e3db8e28 100644
--- a/weed/mount/page_writer.go
+++ b/weed/mount/page_writer.go
@@ -29,14 +29,14 @@ func newPageWriter(fh *FileHandle, chunkSize int64) *PageWriter {
 	return pw
 }
 
-func (pw *PageWriter) AddPage(offset int64, data []byte, isSequentail bool) {
+func (pw *PageWriter) AddPage(offset int64, data []byte, isSequential bool) {
 
 	glog.V(4).Infof("%v AddPage [%d, %d)", pw.fh.fh, offset, offset+int64(len(data)))
 
 	chunkIndex := offset / pw.chunkSize
 	for i := chunkIndex; len(data) > 0; i++ {
 		writeSize := min(int64(len(data)), (i+1)*pw.chunkSize-offset)
-		pw.addToOneChunk(i, offset, data[:writeSize], isSequentail)
+		pw.addToOneChunk(i, offset, data[:writeSize], isSequential)
 		offset += writeSize
 		data = data[writeSize:]
 	}
diff --git a/weed/mount/page_writer_pattern.go b/weed/mount/page_writer_pattern.go
index 665056b36..1ec9c9d4c 100644
--- a/weed/mount/page_writer_pattern.go
+++ b/weed/mount/page_writer_pattern.go
@@ -1,9 +1,9 @@
 package mount
 
 type WriterPattern struct {
-	isStreaming     bool
-	lastWriteOffset int64
-	chunkSize       int64
+	isSequentialCounter int64
+	lastWriteStopOffset int64
+	chunkSize           int64
 }
 
 // For streaming write: only cache the first chunk
@@ -12,33 +12,21 @@ type WriterPattern struct {
 
 func NewWriterPattern(chunkSize int64) *WriterPattern {
 	return &WriterPattern{
-		isStreaming:     true,
-		lastWriteOffset: -1,
-		chunkSize:       chunkSize,
+		isSequentialCounter: 0,
+		lastWriteStopOffset: 0,
+		chunkSize:           chunkSize,
 	}
 }
 
 func (rp *WriterPattern) MonitorWriteAt(offset int64, size int) {
-	if rp.lastWriteOffset > offset {
-		rp.isStreaming = false
+	if rp.lastWriteStopOffset == offset {
+		rp.isSequentialCounter++
+	} else {
+		rp.isSequentialCounter--
 	}
-	if rp.lastWriteOffset == -1 {
-		if offset != 0 {
-			rp.isStreaming = false
-		}
-	}
-	rp.lastWriteOffset = offset
+	rp.lastWriteStopOffset = offset + int64(size)
 }
 
-func (rp *WriterPattern) IsStreamingMode() bool {
-	return rp.isStreaming
-}
-
-func (rp *WriterPattern) IsRandomMode() bool {
-	return !rp.isStreaming
-}
-
-func (rp *WriterPattern) Reset() {
-	rp.isStreaming = true
-	rp.lastWriteOffset = -1
+func (rp *WriterPattern) IsSequentialMode() bool {
+	return rp.isSequentialCounter >= 0
 }
diff --git a/weed/mount/weedfs_file_write.go b/weed/mount/weedfs_file_write.go
index d14680752..2b7a6cea2 100644
--- a/weed/mount/weedfs_file_write.go
+++ b/weed/mount/weedfs_file_write.go
@@ -58,7 +58,7 @@ func (wfs *WFS) Write(cancel <-chan struct{}, in *fuse.WriteIn, data []byte) (wr
 	entry.Attributes.FileSize = uint64(max(offset+int64(len(data)), int64(entry.Attributes.FileSize)))
 	// glog.V(4).Infof("%v write [%d,%d) %d", fh.f.fullpath(), req.Offset, req.Offset+int64(len(req.Data)), len(req.Data))
 
-	fh.dirtyPages.AddPage(offset, data, fh.dirtyPages.writerPattern.IsStreamingMode())
+	fh.dirtyPages.AddPage(offset, data, fh.dirtyPages.writerPattern.IsSequentialMode())
 
 	written = uint32(len(data))
 
diff --git a/weed/shell/command_s3_configure.go b/weed/shell/command_s3_configure.go
index ddcafd847..0660b7889 100644
--- a/weed/shell/command_s3_configure.go
+++ b/weed/shell/command_s3_configure.go
@@ -2,6 +2,7 @@ package shell
 
 import (
 	"bytes"
+	"errors"
 	"flag"
 	"fmt"
 	"github.com/chrislusf/seaweedfs/weed/filer"
@@ -164,6 +165,17 @@ func (c *commandS3Configure) Do(args []string, commandEnv *CommandEnv, writer io
 		s3cfg.Identities = append(s3cfg.Identities, &identity)
 	}
 
+	accessKeySet := make(map[string]string)
+	for _, ident := range s3cfg.Identities {
+		for _, cred := range ident.Credentials {
+			if userName, found := accessKeySet[cred.AccessKey]; !found {
+				accessKeySet[cred.AccessKey] = ident.Name
+			} else {
+				return errors.New(fmt.Sprintf("duplicate accessKey[%s], already configured in user[%s]", cred.AccessKey, userName))
+			}
+		}
+	}
+
 	buf.Reset()
 	filer.ProtoToText(&buf, s3cfg)
 
diff --git a/weed/storage/disk_location.go b/weed/storage/disk_location.go
index 847324838..a2a63acbb 100644
--- a/weed/storage/disk_location.go
+++ b/weed/storage/disk_location.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"sync"
 	"time"
@@ -206,7 +207,11 @@ func (l *DiskLocation) concurrentLoadingVolumes(needleMapKind NeedleMapKind, con
 
 func (l *DiskLocation) loadExistingVolumes(needleMapKind NeedleMapKind) {
 
-	l.concurrentLoadingVolumes(needleMapKind, 10)
+	workerNum := runtime.NumCPU()
+	if workerNum <= 10 {
+		workerNum = 10
+	}
+	l.concurrentLoadingVolumes(needleMapKind, workerNum)
 	glog.V(0).Infof("Store started on dir: %s with %d volumes max %d", l.Directory, len(l.volumes), l.MaxVolumeCount)
 
 	l.loadAllEcShards()