On 2/14/10 4:12 PM, Kjetil Torgrim Homme wrote:
Bogdan Ćulibrk<b...@default.rs> writes:
What are my options from here? To move onto zvol with greater
blocksize? 64k? 128k? Or I will get into another trouble going that
way when I have small reads coming from domU (ext3 with default
blocksize of 4k)?
yes, definitely. have you considered using NFS rather than zvols for
the data filesystems? (keep zvol for the domU software.)
it's strange that you see so much write activity during backup -- I'd
expect that to do just reads... what's going on at the domU?
Most likely the cause of the whole problem - not having noatime set for all
domU and dom0 filesystems. During backups of the domUs you will be constantly
thrashing doing writes to all your metadata for nothing.
On the dom0, if you don't have noatime on, you are constantly updating the
metadata for the domU backing store, since they generally have some read
traffic all the time.
generally, the best way to improve performance is to add RAM for ARC
(512 MiB is *very* little IMHO) and SSD for your ZIL, but it does seem
to be a poor match for your concept of many small low-cost dom0's.
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