thanks this is perfect...yeah, we want 4 nodes(2 in each data center) so just a bit more than 3 ;) so we can have both datacenters be active at the same time and not have to write to the other datacenter except in the background. This is perfect......hbase couldn't do this which I wanted badly along with the in-memory write and write to disk in the background. thanks!!!! Dean
On Sun, Jul 24, 2011 at 4:40 PM, aaron morton <aa...@thelastpickle.com>wrote: > 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 >> > > >
