On Fri, Sep 4, 2009 at 4:05 PM, Michael Stowe
<[email protected]>wrote:
>
> It's an awfully good question, but there probably isn't a single right
> answer. My server is a quad-cpu beast on a gigabit network, but I settled
> on two backups at a time after measuring degradation (first back up one at
> a time, then two, then three...) Then again, neither my file system nor
> server is dedicated, and for me, that means that other I/O bound processes
> don't have trouble running.
>
> Naturally, your I/O wait will be higher if your CPU's are faster, and load
> average can be nonsensical if you're significantly I/O bound -- so I'd
> recommend doing something similar to what I did -- namely, try one backup
> at a time, then ratchet up the number until they slow down too much.
>
> Filesystem type and physical storage structure are significant in how much
> I/O overhead you've got.
>
>
I have to agree. you will need to just start at 1 and move up.
What filesystem are you using? some are faster than others. If you are
using ext3 then I suggest you try XFS.
Also, do you know what IO scheduler you are using? This can determin how
gracefull your system behaves during high IO loads and can help keep your
system load in check.
How are your disks setup? Are you doing raid? if you are doing raid5 or
raid6, especially in software, that is a major point of slowdown. raid5/6
does a checksum that hurts performance significantly. Your best bet is to
do either a raid1 mirror, or a raid10. no checksum while keeping
redundancy.
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