cache empties itself?

Sascha Ottolski ottolski at
Fri Apr 4 12:20:59 CEST 2008

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> 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

More information about the varnish-misc mailing list