Clustering of Varnish Cache

Per Buer perbu at
Tue Nov 6 12:44:01 CET 2012


On Tue, Nov 6, 2012 at 12:27 PM, Soumendu Bhattacharya <
soumendu_bhattacharya at> wrote:

> **
> Can someone please highlight if Varnish can do the following :****
> ** **
> **1.       **Varnish Cache clustering (ie different physical servers
> hosting Varnish will share the same cache among them ). If this is doable ,
> can someone give a brief of how they have implemented this. Currently we
> have only tested Varnish with cache as malloc or file .
No. Varnish servers can't share cache. You probably don't need this if you
set up stuff right. You might want to hash incoming requests on the URL so
you don't get any cache duplication. If you are worried about sudden drops
in hit rate if a server should fail you might want to look into a setup
with some depth (ie two layers of cache). However, my recommendation is to
keep things simple. Varnish is fairly robust and once it is up and running
it tends to stay that way.

> **2.       **Can the above be done if Persistent Store is used (i.e cache
> clustering using Persistent Store). ? if yes, would be really obliged if
> someone can provide some pointers as to how to set this up.

> ****
> **3.       **Is Persistent store an option for a Production environment ?
> ( read somewhere that its experimental).

We have people running it in production for certain workloads and it is
stable. However, the cache semantics would be FIFO and not LRU and that
might not suite your workload.

> ****
> **
 <> *Per Buer*
CEO | Varnish Software AS
Phone: +47 958 39 117 | Skype: per.buer
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