diskio low read performance

Mark Kirkwood markir at paradise.net.nz
Fri Jan 12 22:13:17 PST 2007

Michel Santos wrote:
> I hope somebody can help me. I upgraded recently my cache server (squid)
> 4.11 to 6.2
> I notice that my disk read performance seems to be low. I observe it by
> reading diskio from net-snmp. I started to check this because my old
> server gave much better results from cache.
> I see read access as 1/4 - 1/6 of write access. My cache_dirs are full and
> no swap in use. IOLA is not over 25-30 in peaks
> is there some special configuration to get better read performance on 6.2?
> My disks are UW320 10k on Adaptec 29320 and the same as on the 4.11
> server. I really dont care about write speed so much so if there are
> parameters to configure I apreciate to hear about.
> I checked the following with 1 and 0 but it does not make any difference
> at all
> vfs.write_behind
> vfs.vmiodirenable
> I get an average of 6-8Mb/s through this server and 3-4 of it is http
> traffic. I see the object are going into the cache but for some reason it
> seems they can not be read in time.
> I tried different newfs -b and -f and actually 1024/4096 seems to be best.
> I do not cache large files on this machine.
> Is there something I sgould try?

Note sure this will help you, as your files are all small, but try 
increasing vfs.read_max (say 16 or 32).



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