[Bug 8512] New: rsync -a slower than cp -a

samba-bugs at samba.org samba-bugs at samba.org
Fri Oct 7 08:23:36 MDT 2011


           Summary: rsync -a slower than cp -a
           Product: rsync
           Version: 3.1.0
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P5
         Component: core
        AssignedTo: wayned at samba.org
        ReportedBy: linux.news at bucksch.org
         QAContact: rsync-qa at samba.org

1. du /foo/bigfile
2. echo 3 > /proc/sys/vm/drop_caches
3. time rsync -avp /foo/bigfile /bar/bigfile
4. echo 3 > /proc/sys/vm/drop_caches
5. time cp -a /foo/bigfile /bar/bigfile

Actual result:
1. ~1286 MB
3. 27.9s, 45.9 MB/s per calc, 45.61 MB/s according to rsync
5. 14.6s, 88.1 MB/s per calc

In other words, cp is *almost twice as fast* as rsync. On a single big file
where no comparison is necessary.

Expected result:
When copying a file, rsync is as fast as cp.

rsync is great, but this is a real putoff. I don't see a good reason either, as
the two programs perform the same function in this case. Must be some design
problem. Find the bottleneck and eliminate it, please.

rsync advertizes with its speed.

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