Assuming you need to work with quorum in a non-vnode scenario. That means that if 2 nodes in a row in the ring are down some number of quorum operations will fail with UnavailableException (TimeoutException right after the failures). This is because the for a given range of tokens quorum will be impossible, but quorum will be possible for others.
In a vnode world if any two nodes are down, then the intersection of vnode token ranges they have are unavailable. I think it is two sides of the same coin. On Mon, Dec 10, 2012 at 7:41 AM, Richard Low <r...@acunu.com> wrote: > Hi Tyler, > > You're right, the math does assume independence which is unlikely to be > accurate. But if you do have correlated failure modes e.g. same power, > racks, DC, etc. then you can still use Cassandra's rack-aware or DC-aware > features to ensure replicas are spread around so your cluster can survive > the correlated failure mode. So I would expect vnodes to improve uptime in > all scenarios, but haven't done the math to prove it. > > Richard. >
