increased filesystem read buffer to speedup writes

tools/filesystem/blob/reader.go

@@ -173,7 +173,7 @@ func (r *Reader) WriteTo(w io.Writer) (int64, error) {
 func readFromWriteTo(r io.Reader, w io.Writer) (int64, int64, error) {
 	// Note: can't use io.Copy because it will try to use r.WriteTo
 	// or w.WriteTo, which is recursive in this context.
-	buf := make([]byte, 1024)
+	buf := make([]byte, 4096)
 	var totalRead, totalWritten int64
 	for {
 		numRead, rerr := r.Read(buf)