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Re: Low HIT ratio with Coss

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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

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