Re: Large, busy, caches... problems?

On Wed, 26 Mar 1997, Ian Cooper wrote:

> I would like to increase the cache size (2GB does not give us a
> particularly high hit rate compared to our other machines) - ideally
> to 4.5GB (or higher - the machine has 16GB available!). I have been
> told that if I can show that the problems will be 'resolved' by adding
> memory then it may be possible to purchase an additional 128MB RAM.
>
> Would other users of large, busy, caches care to comment on their
> experiences? (Particularly with respect to the problems encountered
> when paging or operating during the clean cycle.)

We're running two squid 1.1.5 caches with 7.5GB of disc each. One is a
Sparc20 with 192Mb memory and the other an Ultra140 with 256Mb. Both are
coping comfortably with squid process sizes of 119Mb and 190Mb approx.
There are no other applications running on these boxes which use any
significant ammount of memory, so it's rarely paging.

Interestingly the memory accounted for by squid is 67Mb and 62Mb
respectively.

I suspect a large part of your memory consumption will be that used by
in-transit data, though. The latter of our two caches had been stable at
about 167Mb for a week or two before I downloaded some very large objects
several times in quick succession through it, when the usage leapt.

I may be finding a correlation where none exists there though.

Hitrates are in the order of 400,000 UDP and 100,000 TCP requests/day
each.

I've not noticed any slowdown when the cache fills up, but then again each
cache has been sitting a a stable size for ages now between the cache-low
and the cache-high values. I don't think it's ever needed to do an
emergency clear-out.

John
Received on Wed Mar 26 1997 - 10:15:43 MST