diff --git a/src/backup/chunk_stream.rs b/src/backup/chunk_stream.rs
index 040c7c77..fb11ac8d 100644
--- a/src/backup/chunk_stream.rs
+++ b/src/backup/chunk_stream.rs
@@ -4,17 +4,19 @@ use proxmox_protocol::Chunker;
 use futures::{Async, Poll};
 use futures::stream::Stream;
 
+use bytes::BytesMut;
+
 /// Split input stream into dynamic sized chunks
 pub struct ChunkStream<S> {
     input: S,
     chunker: Chunker,
-    buffer: Option<Vec<u8>>,
-    scan: Option<Vec<u8>>,
+    buffer: BytesMut,
+    scan_pos: usize,
 }
 
 impl <S> ChunkStream<S> {
     pub fn new(input: S) -> Self {
-        Self { input, chunker: Chunker::new(4 * 1024 * 1024), buffer: None, scan: None}
+        Self { input, chunker: Chunker::new(4 * 1024 * 1024), buffer: BytesMut::new(), scan_pos: 0}
     }
 }
 
@@ -24,27 +26,24 @@ impl <S> Stream for ChunkStream<S>
           S::Error: Into<Error>,
 {
 
-    type Item = Vec<u8>;
+    type Item = BytesMut;
     type Error = Error;
 
-    fn poll(&mut self) -> Poll<Option<Vec<u8>>, Error> {
+    fn poll(&mut self) -> Poll<Option<BytesMut>, Error> {
         loop {
 
-            if let Some(data) = self.scan.take() {
-                let buffer = self.buffer.get_or_insert_with(|| Vec::with_capacity(1024*1024));
-                let boundary = self.chunker.scan(&data);
+            if self.scan_pos < self.buffer.len() {
+                let boundary = self.chunker.scan(&self.buffer[self.scan_pos..]);
+
+                let chunk_size = self.scan_pos + boundary;
 
                 if boundary == 0 {
-                    buffer.extend(data);
+                    self.scan_pos = self.buffer.len();
                     // continue poll
-                } else if boundary == data.len() {
-                    buffer.extend(data);
-                    return Ok(Async::Ready(self.buffer.take()));
-                } else if boundary < data.len() {
-                    let (left, right) = data.split_at(boundary);
-                    buffer.extend(left);
-                    self.scan = Some(right.to_vec());
-                    return Ok(Async::Ready(self.buffer.take()));
+                } else if chunk_size <= self.buffer.len() {
+                    let result = self.buffer.split_to(chunk_size);
+                    self.scan_pos = 0;
+                    return Ok(Async::Ready(Some(result)));
                 } else {
                     panic!("got unexpected chunk boundary from chunker");
                 }
@@ -58,26 +57,21 @@ impl <S> Stream for ChunkStream<S>
                     return Ok(Async::NotReady);
                 }
                 Ok(Async::Ready(None)) => {
-                    let mut data = self.buffer.take().or_else(|| Some(vec![])).unwrap();
-                    if let Some(rest) = self.scan.take() { data.extend(rest); }
-
-                    if data.len() > 0 {
-                        return Ok(Async::Ready(Some(data)));
+                    self.scan_pos = 0;
+                    if self.buffer.len() > 0 {
+                        return Ok(Async::Ready(Some(self.buffer.take())));
                     } else {
                         return Ok(Async::Ready(None));
                     }
                 }
                 Ok(Async::Ready(Some(data))) => {
-                    let scan = self.scan.get_or_insert_with(|| Vec::with_capacity(1024*1024));
-                    scan.extend(data.as_ref());
-                }
+                    self.buffer.extend_from_slice(data.as_ref());
+                 }
             }
         }
     }
 }
 
-use bytes::BytesMut;
-
 /// Split input stream into fixed sized chunks
 pub struct FixedChunkStream<S> {
     input: S,