Strategy for large cache sets

Calle Korjus calle at
Thu Jul 3 08:21:58 CEST 2008

We are running varnish with a huge dataset (+5TB) on our backends, we've been trying a lot of different setups but we've also ran into the problem with load spikes with every configuration that cahches more than the amount of ram we have, both mmap and malloc with larger swap. Right now we are running trunk with tcmalloc and 55gb cachestore (we have 64gb ram in the frontends now) we have about 70% cachehits and it's very stable, but we're still looking for a way to use mmap or malloc+swap to be able to have a cachestore over 100gb. So I'm also very interested in your results.


-----Original Message-----
From: varnish-misc-bounces at [mailto:varnish-misc-bounces at] On Behalf Of Barry Abrahamson
Sent: den 2 juli 2008 17:59
To: varnish-misc at
Subject: Re: Strategy for large cache sets

On Jul 1, 2008, at 2:16 PM, Skye Poier Nott wrote:

> I want to deploy Varnish with very large cache sizes (200GB or more)
> for large, long lived file sets.

We are doing this also and running into performance problems.  We have
tried files and swap  Running on Linux (Debian).  When the cache
starts to get large, we start to see huge load spikes (loads of 200+)
caused by IO wait but no corresponding spikes in request rates or any
of the varnish metrics (except threads running which I am pretty sure
is a result of the load spike and not the cause).   We are currently
running 1.1.2 but have tried with trunk and the same thing happens.
If you find anything useful in your testing, I would love you hear
about it.

Barry Abrahamson | Systems Wrangler | Automattic

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