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

[pub crawler]

Thanks again Poul for all you do.

How does Varnish handle the hashing and locating of data where a
backend returns to the pool?  Wouldn't the hashing be wrong for prior
loaded items since a machine has returned and the pool widens?

Just trying to figure out the implications of this because in our
environment we regularly find ourselves pulling servers offline.
Wondering if the return of a Varnish would operate like a cold-cache
miss or what magic in Varnish deals with the change in hashing per se.

> It's probably simplest to paraphrase the code:
>
>        Calculate hash over full complement of backends.
>        Is the selected backend sick
>                Calculate hash over subset of healthy backends
>