On Sat, Jan 16, 2010 at 10:44 AM, Poul-Henning Kamp <[email protected]> wrote: > In message <[email protected]>, > 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. Right, but those 2 remaining are at least still being asked for the same url's they were prior to the 1 dying. They're just now responsible for the dead varnish's urls in addition to their own working set. This is much better than the entire url space being hashed against 2 buckets. ...or is my understanding of consistent hashing flawed?
> > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > [email protected] | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > _______________________________________________ > varnish-misc mailing list > [email protected] > http://projects.linpro.no/mailman/listinfo/varnish-misc > _______________________________________________ varnish-misc mailing list [email protected] http://projects.linpro.no/mailman/listinfo/varnish-misc
