Re: [squid-users] Performances: Global rule to size a server

 On Mon, 05 Sep 2011 20:23:02 +0200, David Touzeau wrote:
> Dear
>
> I would like to create a kind of law calculation in order to quickly
> calculate server performances to store squid...
>
> I know there is a lot of parameters that should make e this
> calculation
> more complex, but this is just to be generic.
>

 "generic" is not possible. It boils down to what _your_ users are doing
 is different to _my_ users.

> For example :
>
> I have 150 users :
> -----------------------------------
>
> Memory : 750K per users = 150x750=112 Mb memory + 300Mb for the
> system =
> 512 Mb minimal.
> Hard disk cache : 50Mb/user = 150*50 = 7.5Go minimal stored disk
> size
> for cache..
>
> Is it make sense ?

 Your aim makes sense in a way. The metric of "per user" does not relate
 to resource usage though.

 This is solely because one user could be making no requests at all or
 several thousand per second. And they can switch between these
 behaviours and random values in between without notice. I have seen a
 network happily serving 15K users with one Squid on a 50MBit uplink, and
 also a GigE network brought to its knees by just a few users. "Normal"
 web traffic in both cases.

 The Squid relevant metrics are closer tied to requests per second, or
 the internal Mbps line speed of HTTP requirements.

 Minimal stored disk size is always zero. Maximal is best at <80% of the
 size of the disk you plug in. Moderated by at most 2^24 objects per
 cache_dir. This is a fixed limit, so performance there is relative to
 your average cacheable object size. Disks are best sized along the
 lines of: 2^24 * avg object size. Overall disk count multiply that out
 by req-per-sec to the time you want things cached by or run out of $$ to
 buy disks.

 Memory consumption is dominated by the disk index (10-15 MB index / 1
 GB of storage). And by cache_mem storage, which will suck up every spare
 byte you can give it until itself starts to suffer those 2^24 object
 limits. per-User/connection requirements are measured in KB, so these
 days not really worth worrying over.

 Amos
Received on Tue Sep 06 2011 - 04:15:55 MDT