Re: [squid-users] about the cache and CARP

From: Amos Jeffries <>
Date: Tue, 23 Aug 2011 23:04:56 +1200

On 23/08/11 21:37, Matus UHLAR - fantomas wrote:
> On 16.08.11 16:54, Carlos Manuel Trepeu Pupo wrote:
>> I want to make Common Address Redundancy Protocol or CARP with two
>> squid 3.0 STABLE10 that I have, but here I found this question:
> the CARP that squid supports is the "Cache Array Routing Protocol"
> - this is something different than "Common Address Redundancy Protocol"

Well, technically Squid supports both. Though we generally don't use the
term CARP to talk about the OS addressing algorithms. HA, LVS or NonStop
are usually mentioned directly.

>> If the main Squid with 40 GB of cache shutdown for any reason, then
>> the 2nd squid will start up but without any cache.
>> There is any way to synchronize the both cache, so when this happen
>> the 2nd one start with all the cache ?
> You would need something that would synchronize squid's caches,
> otherwise it would eat two times the bandwidth.


If the second Squid is not running until the event the cache can be
safely mirrored. Though that method will cause a slow DIRTY startup
rather than a fast not-swap. On 40GB it could be very slow, and maybe
worse than an empty cache.

NP: the traffic spike from an empty cache decreases in exponential
proportion to the hit ratio of the traffic. From a spike peak equal to
the internal bandwidth rate.

PS. I have a feeling you might have some graphs to demonstrate that
spike effect Carlos. Would you be able to share the images and numeric
details? I'm looking for details to update the 2002 documentation.


Please be using
   Current Stable Squid 2.7.STABLE9 or 3.1.14
   Beta testers wanted for
Received on Tue Aug 23 2011 - 11:05:07 MDT

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