rsync compression (-z) and timestamp

[Matt McCutchen]

On Thu, 2009-01-29 at 09:43 +0100, David de Lama wrote: 
> YES, the same results! The copy command takes nearly twice as long as the -c command!:(
> I can't explain it!!!
> 
> With the copy command I get following result:
> ================================
> 
> receiving incremental file list
> test/test.xyz
>   1048576000 100%   15.86MB/s    0:01:03 (xfer#1, to-check=0/2)
> 
> Number of files: 2
> Number of files transferred: 1
> Total file size: 1048576000 bytes
> Total transferred file size: 1048576000 bytes
> Literal data: 0 bytes
> Matched data: 1048576000 bytes
> File list size: 45
> File list generation time: 0.013 seconds
> File list transfer time: 0.000 seconds
> Total bytes sent: 226747
> Total bytes received: 129657
> 
> sent 226747 bytes  received 129657 bytes  3581.95 bytes/sec
> total size is 1048576000  speedup is 2942.10
> 
> 
> 
> And with the -c command:
> ==================
> 
> receiving incremental file list
> 
> Number of files: 2
> Number of files transferred: 0
> Total file size: 1048576000 bytes
> Total transferred file size: 0 bytes
> Literal data: 0 bytes
> Matched data: 0 bytes
> File list size: 61
> File list generation time: 0.009 seconds
> File list transfer time: 0.000 seconds
> Total bytes sent: 15
> Total bytes received: 85
> 
> sent 15 bytes  received 85 bytes  1.77 bytes/sec
> total size is 1048576000  speedup is 10485760.00

The first command is transferring the file and the second is not,
because the file has already been transferred.  That's why the first
command is taking longer.  What did you expect to see?

> A question:
> In the copy command above, I get after receiving the incremental file list a transfer rate of 15.86MB/s.
> Is this the speed testing the checksums? Because I set the bwlimit to 10000. Or am I wrong?

As the man page description of --progress says, that rate is the rate at
which the receiver is reconstructing the file, which could be much
higher than the actual bandwidth being used when compression or the
delta-transfer algorithm is enabled.

-- 
Matt