varnish redundancy

andan andan armdan20 at
Thu Sep 3 12:57:17 CEST 2009

2009/9/3 Rob Ayres <quasirob at>:
> Hi,
> We are using varnish on a single server with four backend servers. This is
> working very well (thanks to the varnish developers!) but we wish to add
> some redundancy to the system. The obvious way is just to add another
> varnish running on another server in a different datacentre. The downside to
> this is that keeping two caches populated will increase the load on the
> backend servers.
> We do have the facility to use "backup chaining" which would allow us to use
> varnish_1 and then if that goes down we would automatically failover to
> varnish_2 but this would have an empty cache so a sudden and huge load would
> hit the backend servers.
> Does anyone have any experience or tips on using varnish in this way?

We have two varnish load balanced with LVS (active-active).

The difference between to use 1 or 2 varnish (for the backends load)
is practically zero, because the hit rate
is 90%.

Hope this helps.

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