Re: [squid-users] Hardware configuration for Squid that can handle 100 - 200 Mbps

Gavin McCullagh wrote:
> Hi,
>
> On Thu, 27 Aug 2009, Chris Robertson wrote:
>
>> It will if you can fill them without overloading the cache index. Each
>> object in the cache needs to be indexed in memory. The 10MB of RAM per
>> GB of disk space assumes an average object size of 10KB. Using that
>> rule of thumb, you'd need 100GB of RAM for a 10TB cache (just for the
>> index)!
>
> This rule of thumb may be reasonable, but the average object size seems too
> low to me. We see an 80KB average object size, which suggests something
> more like 1.25MB per GB. We have 1GB as our disk cache max object size
> which doubtless does expand the average. If you want high byte hit rate
> you need to cache large objects.

Whereas I have two caches. One has an average object size of 64KB the
other 128KB. However people from large ISPs are still posting ~10KB avg
object sizes in their stats.

Avg size varies and is highly dependent on the users traffic patterns.
A demographic which spend all their time streaming video would have an
avg object size of MBs.

There are a LOT of objects on the web which are under 10KB of size.

>
> We have an 800GB cache (2x400GB on two 1TB disks) and although there's 8GB
> of ram, it's on a 32-bit operating system (so squid's process size can't go
> above 3GB). The above value suggests the indexes take up about 1GB of RAM.
> We have a 1GB memory cache and all runs fine without swapping so the index
> must be fitting into 2GB.

Its a 4095 MB cap on 32-bit. (4 GB minus 1 KB).

Amos

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