Gavin McCullagh wrote:
Hi,
On Tue, 07 Apr 2009, Amos Jeffries wrote:
Gavin McCullagh wrote:
Mine too. The operating system is on linux software RAID1 partitions so I
Ah, there we probably have the answer as to why there is so much iowait.
I'm not convinced of that. The iowait seems to grow directly as a function
of the cache size and the caches themselves are not RAIDed. You can see
that I recently reduced the cache size and got an immediate, substantial
reduction in iowait.
http://deathcab.gcd.ie/munin/gcd.ie/watcher.gcd.ie.html#Squid
http://deathcab.gcd.ie/munin/gcd.ie/watcher.gcd.ie.html#System
You may want to find out how to determin RAID iowait vs other iowait and
see what shows up.
That would be interesting alright. I'll see what I can find out.
Though I only had 2x 250GB disks on 2.6GHz box RAID1, Squid maxed out
and started seriously lagging requests under 3 users (at around ~5Mbps
wild guess).
Did you have the cache on RAID1 or the OS or both? Hardware or software
RAID (not that my using software should improve anything of course)?
I shifted to a *slower* 1.8GHz box with single OS-shared disk and it now
hits serves 15 users without sweating and runs dozens of reverse-proxy
domains as a side job.
Squid's usage of CPU time doesn't seem to be an issue for us at all so I
can well believe that.
My review of RAID + Squid was overruled by some RAID experts with more
experience. I'm still puzzled how they got the evidence for
"performance: quite good" on software RAID though, maybe dual-core
minimum, mine are both singles.
I can certainly see how putting the cache on software RAID1 is a bad plan,
but that's not what I've done and the iowait is sensitive to cache size.
I have the squid logs and the squid cache on single disk partitions. I
don't think the OS shouldn't be loading the disk too much.
Many thanks for your help on this,
Gavin
ah, got me wires crossed. sorry there.
Amos
--
Please be using
Current Stable Squid 2.7.STABLE6 or 3.0.STABLE13
Current Beta Squid 3.1.0.6
