Slow disk access while rsync - what should I tune?

[Matthew Seaman]

On 24/10/2010 14:15, cronfy wrote:
> I tried to enable async (in hope it will make rsync faster) or even
> disable softupdates on /backup partition (in hope it will make rsync
> slower and OS filesytem cache will not be flushed by backups), it did
> not help. I also want to try to upgrate to Adaptec 5405 (it has 256M
> of write cache) or move mysql databases on a separate SAS disk, but I
> just not quite sure what will help better.

rsync has standard options to limit the bandwidth it will consume.
Making it write through a narrow pipe will also slow down the rate of
disk accesses, so should help control the impact on other services on
the machine.

However, taking backups slowly makes it harder to ensure you have a
consistent backup, so I recommend you investigate snapshotting the
filesystem (well supported for UFS, trivially easy for ZFS) and then
backup the snapshot as slowly as you like.

	Cheers,

	Matthew


-- 
Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
JID: matthew at infracaninophile.co.uk               Kent, CT11 9PW

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