On Fri, Feb 09, 2007 at 09:52:14AM -0600, eBoundHost: Artur wrote:
Quick question. I'm backing up live servers and it would be great if I could "nice" the process on the remote server because backup should not compete with live requests.
Can you offer some insight into how this is best accomplished?
In future, please ask questions on the rsnapshot-discuss mailing list.
There's lots of helpful people on there, and you're likely to get a
quicker response than if you email me directly. Also it's the first
place to hear about bugs and bugfixes. You can subscribe here:
http://lists.sourceforge.net/mailman/listinfo/rsnapshot-discuss
I have CCed my reply there.
Now to your question ...
rsnapshot, being really just a clever wrapper around rsync, performs
like rsync and has all of rsync's limitations. In particular, for
nigh-on all networky syncs, rsync - and hence rsnapshot - is I/O bound,
not CPU bound, and in particular it is usually held up by the network
and not by disks. This means that fiddling with the niceness will have
little effect. If your platform supports ionice, then you might be able
to work with that.
Unfortunately, rsync doesn't help us much as you can't tell it a priority
on the command line. So - and I'm guessing here - you'd need to tackle
the problem on the machines you're backing up by reniceing the process
that rsync talks to on that machine. If you're using rsyncd, then that
needs to be re-niced (or re-ioniced). If, as is more common, you're using
rsync-over-ssh, then you'll need to fiddle with the sshd's niceness.
If you want to preserve network bandwidth thus making more available for
other traffic although at the expense of making rsync even slower, try
fiddling with --bwlimit (see the rsync manpage for details) which you
can specify in rsnapshot's rsync_long_args config option.
I hope that helps!
--
David Cantrell | Enforcer, South London Linguistic Massive
Blessed are the pessimists, for they test their backups
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