> And my application would fall back to ONE. Quorum writes will also fail so I > would also use ONE so that the app stays up. What would I have to do make the > data to redistribute when the broken node is up again? Simply call nodetool > repair on it?
There is 3 mechanisms for that: - hinted handoff: basically, when the node is back up, the other node will send him what he missed. - read-repair: whenever you read a data and an inconsistency is detected (because one node is not up to date), it gets repaired. - calling nodetool repair The two first are automatic, you have nothing to do. Nodetool repair is usually run only periodically (say once a week) to repair some cold data that wasn't dealt with by the two first mechanisms. -- Sylvain > >> If you want Cassandra to send you an answer with only one node up, use >> CL=ONE (as said by David). >> >>> >>>> On Thu, Dec 9, 2010 at 6:05 PM, Sylvain Lebresne <sylv...@yakaz.com> wrote: >>>> I'ts 2 out of the number of replicas, not the number of nodes. At RF=2, >>>> you have >>>> 2 replicas. And since quorum is also 2 with that replication factor, >>>> you cannot lose >>>> a node, otherwise some query will end up as UnavailableException. >>>> >>>> Again, this is not related to the total number of nodes. Even with 200 >>>> nodes, if >>>> you use RF=2, you will have some query that fail (altough much less that >>>> what >>>> you are probably seeing). >>>> >>>> On Thu, Dec 9, 2010 at 5:00 PM, Timo Nentwig <timo.nent...@toptarif.de> >>>> wrote: >>>>> >>>>> On Dec 9, 2010, at 16:50, Daniel Lundin wrote: >>>>> >>>>>> Quorum is really only useful when RF > 2, since the for a quorum to >>>>>> succeed RF/2+1 replicas must be available. >>>>> >>>>> 2/2+1==2 and I killed 1 of 3, so... don't get it. >>>>> >>>>>> This means for RF = 2, consistency levels QUORUM and ALL yield the same >>>>>> result. >>>>>> >>>>>> /d >>>>>> >>>>>> On Thu, Dec 9, 2010 at 4:40 PM, Timo Nentwig <timo.nent...@toptarif.de> >>>>>> wrote: >>>>>>> Hi! >>>>>>> >>>>>>> I've 3 servers running (0.7rc1) with a replication_factor of 2 and use >>>>>>> quorum for writes. But when I shut down one of them >>>>>>> UnavailableExceptions are thrown. Why is that? Isn't that the sense of >>>>>>> quorum and a fault-tolerant DB that it continues with the remaining 2 >>>>>>> nodes and redistributes the data to the broken one as soons as its up >>>>>>> again? >>>>>>> >>>>>>> What may I be doing wrong? >>>>>>> >>>>>>> thx >>>>>>> tcn >>>>> >>>>> >>>> >>> >>> > >
