diff --git a/go/storage/volume.go b/go/storage/volume.go
index 0f781d8d4..b2c8a2337 100644
--- a/go/storage/volume.go
+++ b/go/storage/volume.go
@@ -9,6 +9,7 @@ import (
 	"os"
 	"path"
 	"sync"
+	"time"
 )
 
 const (
@@ -54,61 +55,42 @@ func loadVolumeWithoutIndex(dirname string, id VolumeId) (v *Volume, e error) {
 func (v *Volume) load(alsoLoadIndex bool) error {
 	var e error
 	fileName := path.Join(v.dir, v.Id.String())
-	v.dataFile, e = os.OpenFile(fileName+".dat", os.O_RDWR|os.O_CREATE, 0644)
+	if exists, canRead, canWrite, _ := checkFile(fileName + ".dat"); exists && !canRead {
+		return fmt.Errorf("cannot read Volume Data file %s.dat", fileName)
+	} else if canWrite {
+		v.dataFile, e = os.OpenFile(fileName+".dat", os.O_RDWR|os.O_CREATE, 0644)
+	} else {
+		glog.V(0).Infoln("opening " + fileName + ".dat in READONLY mode")
+		v.dataFile, e = os.Open(fileName + ".dat")
+		v.readOnly = true
+	}
 	if e != nil {
 		if !os.IsPermission(e) {
-			return fmt.Errorf("cannot create Volume Data %s.dat: %s", fileName, e.Error())
-		}
-		if v.dataFile, e = os.Open(fileName + ".dat"); e != nil {
-			return fmt.Errorf("cannot open Volume Data %s.dat: %s", fileName, e.Error())
+			return fmt.Errorf("cannot load Volume Data %s.dat: %s", fileName, e.Error())
 		}
-		glog.V(0).Infoln("opening " + fileName + ".dat in READONLY mode")
-		v.readOnly = true
 	}
+
 	if v.ReplicaType == CopyNil {
 		e = v.readSuperBlock()
 	} else {
 		e = v.maybeWriteSuperBlock()
 	}
 	if e == nil && alsoLoadIndex {
-		var indexFile *os.File
 		if v.readOnly {
-			glog.V(2).Infoln("opening file", fileName+".idx")
-			if indexFile, e = os.Open(fileName + ".idx"); e != nil && !os.IsNotExist(e) {
-				return fmt.Errorf("cannot open index file %s.idx: %s", fileName, e.Error())
-			}
-			if indexFile != nil {
-				glog.V(2).Infoln("check file", fileName+".cdb")
-				if _, err := os.Stat(fileName + ".cdb"); os.IsNotExist(err) {
-					glog.V(0).Infof("converting %s.idx to %s.cdb", fileName, fileName)
-					if e = ConvertIndexToCdb(fileName+".cdb", indexFile); e != nil {
-						glog.V(0).Infof("error converting %s.idx to %s.cdb: %s", fileName, e.Error())
-					} else {
-						indexFile.Close()
-						indexFile = nil
-					}
-				}
-			}
-			glog.V(2).Infoln("open file", fileName+".cdb")
-			if v.nm, e = OpenCdbMap(fileName + ".cdb"); e != nil {
-				if os.IsNotExist(e) {
-					glog.V(0).Infof("Failed to read cdb file %s, fall back to normal readonly mode.", fileName)
-				} else {
-					glog.V(0).Infof("%s.cdb open errro:%s", fileName, e.Error())
-					return e
-				}
+			if v.ensureConvertIdxToCdb(fileName) {
+				v.nm, e = OpenCdbMap(fileName + ".cdb")
+				return e
 			}
 		}
+		var indexFile *os.File
 		if v.readOnly {
 			glog.V(1).Infoln("open to read file", fileName+".idx")
-			indexFile, e = os.OpenFile(fileName+".idx", os.O_RDONLY, 0644)
-			if e != nil {
+			if indexFile, e = os.OpenFile(fileName+".idx", os.O_RDONLY, 0644); e != nil {
 				return fmt.Errorf("cannot read Volume Data %s.dat: %s", fileName, e.Error())
 			}
 		} else {
 			glog.V(1).Infoln("open to write file", fileName+".idx")
-			indexFile, e = os.OpenFile(fileName+".idx", os.O_RDWR|os.O_CREATE, 0644)
-			if e != nil {
+			if indexFile, e = os.OpenFile(fileName+".idx", os.O_RDWR|os.O_CREATE, 0644); e != nil {
 				return fmt.Errorf("cannot write Volume Data %s.dat: %s", fileName, e.Error())
 			}
 		}
@@ -160,11 +142,11 @@ func (v *Volume) maybeWriteSuperBlock() error {
 }
 func (v *Volume) readSuperBlock() (err error) {
 	if _, err = v.dataFile.Seek(0, 0); err != nil {
-		return fmt.Errorf("cannot seek to the beginning of %s: %s", v.dataFile, err)
+		return fmt.Errorf("cannot seek to the beginning of %s: %s", v.dataFile, err.Error())
 	}
 	header := make([]byte, SuperBlockSize)
 	if _, e := v.dataFile.Read(header); e != nil {
-		return fmt.Errorf("cannot read superblock: %s", e)
+		return fmt.Errorf("cannot read superblock: %s", e.Error())
 	}
 	v.SuperBlock, err = ParseSuperBlock(header)
 	return err
@@ -172,7 +154,7 @@ func (v *Volume) readSuperBlock() (err error) {
 func ParseSuperBlock(header []byte) (superBlock SuperBlock, err error) {
 	superBlock.Version = Version(header[0])
 	if superBlock.ReplicaType, err = NewReplicationTypeFromByte(header[1]); err != nil {
-		err = fmt.Errorf("cannot read replica type: %s", err)
+		err = fmt.Errorf("cannot read replica type: %s", err.Error())
 	}
 	return
 }
@@ -221,7 +203,7 @@ func (v *Volume) write(n *Needle) (size uint32, err error) {
 
 	if size, err = n.Append(v.dataFile, v.Version()); err != nil {
 		if e := v.dataFile.Truncate(offset); e != nil {
-			err = fmt.Errorf("%s\ncannot truncate %s: %s", err, v.dataFile, e)
+			err = fmt.Errorf("%s\ncannot truncate %s: %s", err, v.dataFile, e.Error())
 		}
 		return
 	}
@@ -403,3 +385,48 @@ func (v *Volume) copyDataAndGenerateIndexFile(dstName, idxName string) (err erro
 func (v *Volume) ContentSize() uint64 {
 	return v.nm.ContentSize()
 }
+
+func checkFile(filename string) (exists, canRead, canWrite bool, modTime time.Time) {
+	exists = true
+	fi, err := os.Stat(filename)
+	if os.IsNotExist(err) {
+		exists = false
+		return
+	}
+	if fi.Mode()&0400 != 0 {
+		canRead = true
+	}
+	if fi.Mode()&0200 != 0 {
+		canWrite = true
+	}
+	modTime = fi.ModTime()
+	return
+}
+func (v *Volume) ensureConvertIdxToCdb(fileName string) (cdbCanRead bool) {
+	var indexFile *os.File
+	var e error
+	_, cdbCanRead, cdbCanWrite, cdbModTime := checkFile(fileName + ".cdb")
+	_, idxCanRead, _, idxModeTime := checkFile(fileName + ".idx")
+	if cdbCanRead && cdbModTime.After(idxModeTime) {
+		return true
+	}
+	if !cdbCanWrite {
+		return false
+	}
+	if !idxCanRead {
+		glog.V(0).Infoln("Can not read file", fileName+".idx!")
+		return false
+	}
+	glog.V(2).Infoln("opening file", fileName+".idx")
+	if indexFile, e = os.Open(fileName + ".idx"); e != nil {
+		glog.V(0).Infoln("Failed to read file", fileName+".idx !")
+		return false
+	}
+	defer indexFile.Close()
+	glog.V(0).Infof("converting %s.idx to %s.cdb", fileName, fileName)
+	if e = ConvertIndexToCdb(fileName+".cdb", indexFile); e != nil {
+		glog.V(0).Infof("error converting %s.idx to %s.cdb: %s", fileName, fileName, e.Error())
+		return false
+	}
+	return true
+}