Re: [squid-users] squid performance tunning

On 18/08/11 19:40, Drunkard Zhang wrote:
> 2011/8/18 Chen Bangzhong:
>> My cached objects will expire after 10 minutes.
>>
>> Cache-Control:max-age=600
>
> Static content like pictures should cache longer, like 1 day, 86400.

Could also be a whole year. If you control the origin website, set
caching times as large as reasonably possible for each object. With
revalidate settings relevant to its likely replacement needs. And always
send a correct ETag.

With those details Squid and other caches will take care of reducing
caching times to suit the network and disk needs and
updates/revalidation to suit your needs. So please set it large.

>
>> I don't know why there are so many disk writes and there are so many
>> objects on disk.

All traffic goes through either RAM cache or if its bigger than
maximum_object_size_in_memory will go through disks.

 From that info report ~60% of your traffic bytes are MISS responses. A
large portion of that MISS traffic is likely not storable, so will be
written to cache then discarded immediately. Squid is overall
mostly-write with its disk behaviour.

Likely your 10-minute age is affecting this in a big way. The cache will
have a lot of storable object which are stale. Next request they will be
fetched into memory, then replaced by a revalidation REFRESH (near-HIT)
response, which writes new data back to disk later.

>>
>> In addtion, Disk hits as % of hit requests: 5min: 1.6%, 60min: 1.9%
>> is very low.
>
> Maybe cause by disk read timeout. You used too much disk space, you
> can shrink it a little by a little, until disk busy percentage reduced
> to 80% or lower.

Your Squid version is one which will promote HIT objects from disk and
service repeat HITs from memory. Which reducing that disk-hit % a lot
more than earlier squid versions would show it as.

>
>> Can I increase the cache_mem？ or not use disk cache at all?
>
> I used all memory I can use :-)

Indeed, the more the merrier. Unless it is swapping under high load. If
that happens Squid speed goes terrible almost immediately.

Amos

-- 
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