Re: [squid-users] cache size and structure

Riccardo Castellani wrote:
> I'm preparing new squid machine and I'm defining cache size.
> Old squid had 2 entries into "cache_dir directive" :
>
> cache_dir ufs /usr/local/cache/1 3500 128 256
> cache_dir ufs /usr/local/cache/2 2500 128 256
>

I'd strongly suggest using "aufs" instead of "ufs".

> My cache traffic volume (I/O) is about 2 Mbps a week with peaks of 3 Mbps.
> This squid cache is the parent of 2 other squid machines and it gives
> answers to about 1000 users.
>
> 1- I read you suggest 1 cache_dir to same partition, why I can't use 2
> folder in tha same partition ?!
>

You can, but why would you want to? The suggestion is one cache_dir per
spindle to spread the IO load. Putting multiple partitions on one
spindle makes about the same sense as multiple cache_dirs in the same
partition. Access to all of them will be contending for the limited IO
resources available.

> 2- What do you think my caches size ? 3500 and 2550 ?

Depends on your memory load. A larger cache leads to storing more
objects, which requires more memory to track. The suggestion I recall
is "a week's worth of traffic". If you are seeing an average of 2Mbit/s
24 hours a day, seven days a week, that would lead to a cache of around
150GB.

> and its directory structure (128,256) ?!
>

This is entirely dependent on the filesystem you are using and the
number of objects you cache. The goal is to keep the number of files
per directory reasonable, because most filesystems are not optimized for
a "large" ratio (10s of thousands of files per directory).

Chris
Received on Tue Jun 23 2009 - 21:07:26 MDT