At work we have a reasonably busy Varnish cluster. We hooked it up to Graphite to allow near real-time visualization of how busy it is. Here’s a sample of what part of our Graphite dashboard looks like when you look over the past four months:
Varnish
As seen on varnish-misc@varnish-cache.org:
I read one web testimony of a person who used Varnish to scale a site up to almost 200 million page views a month.
I’d like to find someone who has that level of expertise.
At work we have a Varnish cluster which, during the month of March, served over 17 billion requests for an average of 6,400 requests/second.
This cluster contains two physical machines with 24 cores and 192GB of RAM apiece. These machines have tons of spare capacity; their load average peaked at approximately 4. We’ve even considered virtualizing the cluster.
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I recently helped introduce a Varnish cluster at work to offload a significant number of requests from a heavily-trafficked internal web service. This Varnish cluster serves approximately 10,000 requests/second (with peaks in the 20-30,000 requests/second range) 24x7x365.
While working on this project I ran into a few interesting problems with Varnish. The most interesting one I saw was that Varnish would consume more and more RAM until eventually it would consume all the memory on the box and crash. Using varnishstat, we diagnosed that this was due to unbounded growth of transient storage within the Varnish process.
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