Re: [squid-users] Low HIT ratio with Coss

Hi Usman,

usman wrote:
> Hi EveryOne,
>
> I am getting very low Request Hit ratio on squid cache since i
> implemented coss. The caching directories containing coss stripes file
> are filling up very very slow.
>
> /dev/amrd1s1d 16G 136M 15G 1% /cache1
> /dev/amrd2s1d 16G 141M 15G 1% /cache2
> /dev/amrd3s1d 33G 5.9G 24G 20% /cache3

 From what I understand, COSS by default stores smaller objects in
comparison to UFS, AUFS or DISKD.

This may explain why the COSS directories are filling up slowly.

>
> you can see the comparison between diskd and coss directories.
>
> The cache_dir settings are
> cache_dir coss /cache1 12000 max-size=1048576 max-stripe-waste=524288
> membufs=500
> cache_dir coss /cache2 12000 max-size=1048576 max-stripe-waste=524288
> membufs=500
> cache_dir diskd /cache3 28000 16 256 Q1=72 Q2=64

My COSS cache_dir are as follows:

cache_dir coss /cache1/squid/coss 8192 max-size=131072
max-stripe-waste=16384 block-size=1024 membufs=500

>
>
> On other caches with same refresh pattern (total Diskd or Aufs) I get
> around 45 - 55 % Request HIT ratio. Currently its 12 % with coss. The
> caching directories are not fully loaded yet but still I feel its very
> low request hit ratio.

In one of my FreeBSD Squid box utilizing COSS with the following uptime:

Squid Object Cache: Version 2.6.STABLE16
Start Time: Sun, 09 Sep 2007 11:31:49 GMT
Current Time: Thu, 25 Oct 2007 16:33:23 GMT

I get the following results:

         Request Hit Ratios: 5min: 47.3%, 60min: 46.1%
         Byte Hit Ratios: 5min: 17.9%, 60min: 17.5%
         Request Memory Hit Ratios: 5min: 0.2%, 60min: 0.3%
         Request Disk Hit Ratios: 5min: 55.2%, 60min: 54.5%
         Cache Hits: 0.00767 0.00767
         Near Hits: 1.38447 1.31166

>
> Where is something wrong in my Config ?

I am sure that the low HIT ratio is not a Configuration problem.

>
> Also please suggest the size of "block-size" in coss settings, I am
> using FreeBSD 6.2 with UFS2 file system (with default block size of file
> system 16384 bytes).
> RAM is 4 GB, SMP System.

How long has your FreeBSD squid box been running? My advise is to be a
little more patience with COSS. Let the COSS directories get filled up.

I am sure that your request HIT ratios will gradually increase.

>
>
> Regards
> usman
>
>
>

Thanking you...

-- 
With best regards and good wishes,
Yours sincerely,
Tek Bahadur Limbu
System Administrator
(TAG/TDG Group)
Jwl Systems Department
Worldlink Communications Pvt. Ltd.
Jawalakhel, Nepal
http://www.wlink.com.np
http://teklimbu.wordpress.com