diff --git a/go/operation/upload_content.go b/go/operation/upload_content.go
index cae657b2c..27ebb0f5a 100644
--- a/go/operation/upload_content.go
+++ b/go/operation/upload_content.go
@@ -4,10 +4,12 @@ import (
 	"bytes"
 	"encoding/json"
 	"errors"
+	"path/filepath"
 	_ "fmt"
 	"io"
 	"io/ioutil"
 	"log"
+	"mime"
 	"mime/multipart"
 	"net/http"
 )
@@ -29,7 +31,8 @@ func Upload(uploadUrl string, filename string, reader io.Reader) (*UploadResult,
 		log.Println("error copying data", err)
 		return nil, err
 	}
-	content_type := body_writer.FormDataContentType()
+	content_type := mime.TypeByExtension(filepath.Ext(filename))
+  content_type := body_writer.FormDataContentType()
 	if err = body_writer.Close(); err != nil {
 		log.Println("error closing body", err)
 		return nil, err
diff --git a/go/replication/store_replicate.go b/go/replication/store_replicate.go
index 8306a31b4..f6e84e2ef 100644
--- a/go/replication/store_replicate.go
+++ b/go/replication/store_replicate.go
@@ -23,9 +23,9 @@ func ReplicatedWrite(masterNode string, s *storage.Store, volumeId storage.Volum
 		needToReplicate = s.GetVolume(volumeId).NeedToReplicate()
 	}
 	if needToReplicate { //send to other replica locations
-		if r.FormValue("type") != "standard" {
+		if r.FormValue("type") != "replicate" {
 			if !distributedOperation(masterNode, s, volumeId, func(location operation.Location) bool {
-				_, err := operation.Upload("http://"+location.Url+r.URL.Path+"?type=standard", string(needle.Name), bytes.NewReader(needle.Data))
+				_, err := operation.Upload("http://"+location.Url+r.URL.Path+"?type=replicate&ts="+strconv.FormatUint(needle.LastModified,10), string(needle.Name), bytes.NewReader(needle.Data))
 				return err == nil
 			}) {
 				ret = 0
@@ -39,7 +39,7 @@ func ReplicatedWrite(masterNode string, s *storage.Store, volumeId storage.Volum
 				volumeId.String() + ": " + err.Error()
 		} else {
 			distributedOperation(masterNode, s, volumeId, func(location operation.Location) bool {
-				return nil == operation.Delete("http://"+location.Url+r.URL.Path+"?type=standard")
+				return nil == operation.Delete("http://"+location.Url+r.URL.Path+"?type=replicate")
 			})
 		}
 	}
@@ -59,9 +59,9 @@ func ReplicatedDelete(masterNode string, store *storage.Store, volumeId storage.
 		needToReplicate = store.GetVolume(volumeId).NeedToReplicate()
 	}
 	if needToReplicate { //send to other replica locations
-		if r.FormValue("type") != "standard" {
+		if r.FormValue("type") != "replicate" {
 			if !distributedOperation(masterNode, store, volumeId, func(location operation.Location) bool {
-				return nil == operation.Delete("http://"+location.Url+r.URL.Path+"?type=standard")
+				return nil == operation.Delete("http://"+location.Url+r.URL.Path+"?type=replicate")
 			}) {
 				ret = 0
 			}
diff --git a/go/storage/needle.go b/go/storage/needle.go
index 9c0acc6b9..9822e5d01 100644
--- a/go/storage/needle.go
+++ b/go/storage/needle.go
@@ -90,7 +90,10 @@ func NewNeedle(r *http.Request) (n *Needle, e error) {
 		}
 		n.SetHasName()
 	}
-	n.LastModified = uint64(time.Now().Unix())
+	var parseError error
+	if n.LastModified, parseError = strconv.ParseUint(r.FormValue("ts"), 10, 64); parseError != nil {
+		n.LastModified = uint64(time.Now().Unix())
+	}
 	n.SetHasLastModifiedDate()
 
 	n.Data = data
diff --git a/go/weed/upload.go b/go/weed/upload.go
index a47551ddf..96b326a39 100644
--- a/go/weed/upload.go
+++ b/go/weed/upload.go
@@ -66,7 +66,12 @@ func upload(filename string, server string, fid string) (int, error) {
 		debug("Failed to open file:", filename)
 		return 0, err
 	}
-	ret, e := operation.Upload("http://"+server+"/"+fid, path.Base(filename), fh)
+	fi, fiErr := fh.Stat()
+	if fiErr!=nil {
+    debug("Failed to stat file:", filename)
+    return 0, fiErr
+	}
+	ret, e := operation.Upload("http://"+server+"/"+fid+"?ts="+strconv.Itoa(int(fi.ModTime().Unix()) ), path.Base(filename), fh)
 	if e != nil {
 		return 0, e
 	}
diff --git a/go/weed/volume.go b/go/weed/volume.go
index 039212793..d6c0af123 100644
--- a/go/weed/volume.go
+++ b/go/weed/volume.go
@@ -149,7 +149,7 @@ func GetOrHeadHandler(w http.ResponseWriter, r *http.Request, isGetMethod bool)
 		w.Header().Set("Last-Modified", time.Unix(int64(n.LastModified), 0).UTC().Format(http.TimeFormat))
 		if r.Header.Get("If-Modified-Since") != "" {
 			if t, parseError := time.Parse(http.TimeFormat, r.Header.Get("If-Modified-Since")); parseError == nil {
-				if t.Unix() <= int64(n.LastModified) {
+				if t.Unix() >= int64(n.LastModified) {
 					w.WriteHeader(http.StatusNotModified)
 					return
 				}