Sorry, the title of this thread has to be "*Minimum cluster size to survive a single node failure*".
On Wed, Jun 18, 2014 at 11:38 AM, Prabath Abeysekara < prabathabeysek...@gmail.com> wrote: > Hi Everyone, > > First of all, apologies if the $subject was discussed previously in this > list before. I've already gone through quite a few email trails on this but > still couldn't find a convincing answer which really made me raise this > question again here in this list. > > If my understanding is correct, a *3 node Cassandra cluster* would > survive a single node failure while the Replication Factor is set to 3 with > consistency levels are assigned QUORUM for read/write operations. For > example, let's consider the following configuration. > > * Number of nodes in the cluster : 3 > * Replication Factor : 3 > * Read/Write consistencies : QUORUM (this evaluates to 2 when RF is set to > 3) > > Here's how I expect it to work. > > Whenever a read operation takes place, the Cassandra cluster coordinator > node that receives the read request would try to read from at least two > replicas before responding to the client. With Read consistency being 2 (+ > all raws being available in all three nodes), we should be able to survive > a single node failure in this particular instance for read operations. > Similarly, for write requests, even in the middle of a single node failure, > the writes should be allowed as the Write consistency is set to 2? > > Can someone please confirm whether what's mentioned above is correct? > (Please note that I'm trying to figure out the *minimum* node numbers and > I indeed am aware of the fact that there are other factors also to be > considered in order to come up with the most optimal numbers for a given > cluster requirement). > > > Cheers, > Prabath > -- > Prabath > -- Prabath
