Proxy Cache: how much shared memory is "enough"?

[Maxim Dounin]

Hello!

On Mon, Dec 10, 2012 at 10:37:30PM +0100, Christian Bönning wrote:

> I'm planning to deploy some big websites which will make heavy usage of
> proxy cacheing (e.g. 1.5 million actively accessed objects in cache). The
> ratio of plain HTML vs images should be about 50/50 if that does have any
> impact on the scenario itself. Now the question which came up is how much
> Shared Memory for such a cache is enough. The docs don't really say very
> much about that. So may be one of you can give me a hint on how much memory
> is suitable for such a deployment.

Each object in cache uses 128 bytes of memory in keys shared 
memory zone on 64-bit platforms, as outlined on wiki here:

http://wiki.nginx.org/HttpProxyModule#proxy_cache_path

So for 1.5 mln objects you'll need about 200M of memory.

-- 
Maxim Dounin
http://nginx.com/support.html