Strategies for splitting load across varnish instances? And avoiding single-point-of-failure?

Michael Fischer michael at
Sat Jan 16 19:45:55 CET 2010

On Sat, Jan 16, 2010 at 10:44 AM, Poul-Henning Kamp <phk at>wrote:

> In message <d002c4031001160929p1f688fc9mcc927dda2c684b86 at>,
> Micha
> el Fischer writes:
> >For instance sizes larger than 2, I think a consistent hash is needed.
> > Otherwise, the overall hit ratio will fall dramatically upon failure of
> an
> >instance as the requests are rerouted.
> If you have perfect 1/3 splitting between 3 varnishes, having one die
> will do bad things to your hitrate until the remaining two distribute
> the load between them.
> That's a matter of math, and has nothing to do with the hash algorithm.

Let me put it this way and leave the math up to you:  it will be way worse
if you don't use a consistent hash.

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