cache empties itself?

[Sascha Ottolski]

Am Freitag 04 April 2008 11:50:51 schrieb Michael S. Fischer:
> On Thu, Apr 3, 2008 at 8:59 PM, Ricardo Newbery 
<ric at digitalmarbles.com> wrote:
> >  Well, first of all you're setting up a false dichotomy.  Not
> > everything fits neatly into your apparent definitions of dynamic
> > versus static.  Your definitions appear to exclude the use case
> > where you have cacheable content that is subject to change at
> > unpredictable intervals but which is otherwise fairly "static" for
> > some length of time.
>
> In my experience, you almost never need a caching proxy for this
> purpose.  Most modern web servers are perfectly capable of serving
> static content at wire speed.  Moreover, if your origin servers have
> a reasonable amount of RAM and the working set size is relatively
> small, the static objects are already likely to be in the buffer
> cache.  In a scenario such as this, having caching proxies upstream
> for these sorts of objects can actually be *worse* in terms of
> performance -- consider the wasted time processing a cache miss for
> content that's already cached downstream.
>
> Best regards,
>
> --Michael

you are right, _if_ the working set is small. in my case, we're talking 
20+ mio. small images (5-50 KB each), 400+ GB in total size, and it's 
growing every day. access is very random, but there still is a good 
amount of "hot" objects. and to be ready for a larger set it cannot 
reside on the webserver, but lives on a central storage. access 
performance to the (network) storage is relatively slow, and our 
experiences with mod_cache from apache were bad, that's why I started 
testing varnish. 

and so far, it works amazingly! my main problem remains that it randomly 
crashed, and that the cache file isn't persistent across restarts.

Cheers, Sascha