Re: [squid-users] Large Files and Reverse proxy

Simon Waters wrote:
> On Friday 29 August 2008 03:40:21 Amos Jeffries wrote:
>>> For various reasons we have a number of multimedia files on this end of
>>> the
>>> connection, all large, and all with no explicit expiry information (which
>>> I
>>> can adjust if it helps).
>> That will help. Enormously. The longer it can be explicitly known
>> cacheable the better (RRC states only up to a year though).
>
> Can I ask why? Is the default "LRU" or "heap LFUDA" policy concerned with
> expiry dates.

With known expiry info, squid can calculate fresh/stale properly.
Without it Squid has to estimate and periodically refreshes the object.

The LRU/LFUDA algorithms are only related to garbage collection on
objects in the cache.

refresh_pattern can tune the freshness estimation algorithm in your
cache. But nothing beats proper authoritative info about an objects
freshness. Since that will affect every cache on the web.

>
>>> However are there other likely "gotchas" with handling larger files?
>> Some people find it more efficient to store them on disk rather than in
>> memory. If your squid is already 64-bit or handling it nicely then no
>> problem.
>
> I don't think there is a performance issue here with memory. I think it is
> just down to how the proxy decides which files to keep. As I said the goal is
> to offload bandwidth usage.

Theres an issue ion Squid-2.x related to the size of memory chunks that
can play badly with very large files. If you are not seeing that, then fine.

>
> I'm pondering dropping the caching of small objects, since mostly they cause a
> refresh_hit in this reverse proxy configuration, and the saving on bandwidth
> isn't huge (although presumably it saves a trip over a congested link).
>
> There is also a large number of small image files which I believe can have a
> long expiry date set in Apache, I just need to check that with the guy who
> did the file naming algorithmn. This would probably be a bigger win.
>
> Perhaps I just need a cache which is as larger than all the data to be
> served - which might be possible to organise given the current price of disk
> space.

Amos

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