[squid-users] Re: latency issues squid2.7 WCCP

The latency should be your disk caches, and I'm also assuming that the
sheer size of them could be contributing to it. Also remember that
RAID-0 (or similar) won't help improve performance (since it's access
times that you need, not throughput). We have a much smaller load here
(one machine peaks at around 1100 users), and switching from 7200rpm
SATA drives to 15k SCSI drives solved a lot of latency issues.

One thing you can do is use the max_open_disk_fds value; we found that
our SATA machines had major performance issues when over 50 file
descriptors were currently open. That parameter tells Squid to bypass
the disk cache if the number of open fd's is over that value (that would
definitely help during peak times). You can find the current number of
open fd's in the "Store Disk file open" value in your cachemgr general
runtime page.

Also I'd recommend greatly decreasing the size of your disk caches, and
increasing the cache_mem value (since you have 32 gigs of RAM, I'd
probably try to get the Squid process up to around 30 gigs).

Ryan Thoryk

Ryan Goddard wrote:
>
> Thanks for the response, Adrian.
> Is recompile required to change to internal DNS?
> I've disabled ECN, pmtu_disc and mtu_probing.
> cache_dir is as follows:
> (recommended by Henrik)
>> cache_dir aufs /squid0 125000 128 256 cache_dir aufs /squid1 125000
>> 128 256
>> cache_dir aufs /squid2 125000 128 256
>> cache_dir aufs /squid3 125000 128 256
>> cache_dir aufs /squid4 125000 128 256
>> cache_dir aufs /squid5 125000 128 256
>> cache_dir aufs /squid6 125000 128 256
>> cache_dir aufs /squid7 125000 128 256
>
> No peak data available, here's some pre-peak data:
> Cache Manager menu
> 5-MINUTE AVERAGE
> sample_start_time = 1222199580.85434 (Tue, 23 Sep 2008 19:53:00 GMT)
> sample_end_time = 1222199905.507274 (Tue, 23 Sep 2008 19:58:25 GMT)
> client_http.requests = 268.239526/sec
> client_http.hits = 111.741117/sec
> client_http.errors = 0.000000/sec
> IOSTAT shows lots of idle time - I'm unclear what you mean by
> "profiling" ?
> Also, have not tried running w/out any cache - can you explain
> how this is done?
>
> appreciate the assistance.
> -Ryan
Received on Fri Sep 26 2008 - 18:20:14 MDT