Quick reminder, with RF == 2 the QUORUM is 2 as well. So when using LOCAL_QUORUM with RF 2+2 you will effectively be using LOCAL_ALL which may not be what you want. As De La Soul sang, 3 is the magic number for minimum fault tolerance (QUORUM is then 2).
Cheers ----------------- Aaron Morton Freelance Cassandra Developer @aaronmorton http://www.thelastpickle.com On 23 Jul 2011, at 10:04, Sameer Farooqui wrote: > It sounds like what you're looking for is write consistency of local_quorum: > http://www.datastax.com/docs/0.8/consistency/index#write-consistency > > local_quorum would mean the write has to be successful on a majority of nodes > in DC1 (so 2) before it is considered successful. > > If you use just quorum write, it'll have to be committed to 3 replicas out of > the 4 before it's considered successful. > > > > > On Fri, Jul 22, 2011 at 1:57 PM, Dean Hiller <d...@alvazan.com> wrote: > Ideally, we would want to have a replication factor of 4, and a minimum write > consistency of 2 (which looking at the default in cassandra.yaml is to memory > first with asynch to disk...perfect so far!!!) > > Now, obviously, I can get the partitioner setup to make sure I get 2 replicas > in each data center. The next thing I would want to guarantee however is > that if a write came into datacenter 1, it would write to the two nodes in > datacenter 1 and asynchronously replicate to datacenter 2. Is this possible? > Does cassandra already handle that or is there something I could do to get > cassandra to do that? > > In this mode, I believe I can have both datacenters be live as well as be > backup for the other not wasting resources. > > thanks, > Dean >
