Re: [squid-users] Re: cache memory?

On 29.05.2012 09:45, Beto Moreno wrote:
> Sorry, I didn't finish this post.
>
> 1 question, I will setup a cache server with squid 2.7.x, the server
> will have 8GB of ram, the biggest service will be squid, I'm thinking
> in 4GB for squid, 4GB other services.
> I have seen that squid use part of the memory to save objects and
> some
> times he return the cache from memory or disk, memory is faster we
> know this, them this is one reason
> that I want to give more memory to squid.
>
> Is what I understand, them if I'm right, what happen once U reboot my
> server?
>
> What does squid to the object in memory?

Squid tries to save what it can and terminate cleanly in the time
allowed (shutdown_timeout).

> Do I lost them?

There is a very important concept to keep in mind here which is often
overlooked:

  *** Cache is temporary storage ***. Emphasis on "temporary". It is
Constantly renewed from network sources.

As a result no content is ever "lost". Even should you completely erase
the cache contents and restart from a clean-slate, everything is still
available from the relevant origins/master server somewhere out on the
network.

> Or haven't understand how squid use the memory?

You seem to understand the usage okay. But you are fixated a bit on
hoarding data.

The only side-effect of rebooting the server is a short "full" outage
of service, and a short period of slightly slower service as the caches
are re-filled.

This may sound bad at first glance, but it is a tradeoff between
network and disk re-builds. Even if everything was saved to disk across
the reboot there is still a slow period from disk I/O latency and CPU to
re-populate the memory indexes. Versus network lag of fetching a clean
copy.

Squid has automatic client new-connection damping/buffering to cope
with both these periods and DoS situations without actually loosing
clients requests.

Amos
Received on Tue May 29 2012 - 00:48:03 MDT