[plug] rsync and nfs

[Nick Bannon]

On Sat, Oct 19, 2002 at 12:26:20PM +0800, Bernard Blackham wrote:
[...]
> 	rsync -avx --delete / /backups/machine/
> And the thought just dawned on me - am I actually gaining anything
> by using rsync? The comparison is still done over the network
[...]

What you want is the -W flag, which turns _off_ the funky rsync
checksumming.  What you gain is "rsync the handy mirroring program",
which will copy files if they've changed size/date. The checksumming
and incremental transfer isn't doing you any good - currently, it has
to read the entire source and destination files, across the network,
just to see what changed, then write a new destination file.

 -W, --whole-file            copy whole files, no incremental checks

When copying files on the "local" machine (including NFS) this is
actually the default on the current rsync, but not on older ones (e.g.
rsync 2.4.6, which might be what you're running now).

With the -W, rsync might run on the server, in the available memory,
which will speed things up, and certainly take less CPU. The rsync
algorithm lets you trade off (CPU+disc) bandwidth against network
bandwidth - given a fast network, that's not such a useful tradeoff.

Nick.

-- 
     Nick Bannon      | "I made this letter longer than usual because
  nick-sig at rcpt.to    | I lack the time to make it shorter." - Pascal
http://linux.conf.au/ |  Australian Linux Technical Conference, 2003