> In general we want to achieve strong consistency. You need to have R + W > N
> LOCAL_QUORUM and reads with ONE. Gives you 2 + 1 > 2 when you use it. When you drop back to ONE / ONE you no longer have strong consistency. > may be advise on how to improve it. Sounds like you know how to improve it :) Things you could play with: * hinted_handoff_throttle_delay_in_ms in YAML to reduce the time it takes for HH delay to deliver the messages. * increase the read_repair_chance for the CF's. This will increase the chance of RR repairing an inconsistency behind the scenes, so the next read is consistent. This will also increase the IO load on the system. With the RF 2 restriction you are probably doing the best you can. You are giving up consistency for availability and partition tolerance. The best thing to do to get peeps to agree that "we will accept reduced consistency for high availability" rather than say "in general we want to achieve strong consistency". Hope that helps. ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 9/09/2012, at 9:09 PM, Sergey Tryuber <stryu...@gmail.com> wrote: > Hi > > We have to use Cassandra with RF=2 (don't ask why...). There are two > datacenters (RF=2 in each datacenter). Also we use Astyanax as a client > library. In general we want to achieve strong consistency. Read performance > is important for us, that's why we perform writes with LOCAL_QUORUM and reads > with ONE. If one server is down, we automatically switch to Writes.ONE, > Reads.ONE only for that replica which has failed node (we modified Astyanax > to achieve that). When the server comes back, we turn back > Writes.LOCAL_QUORUM and Reads.ONE, but, of course, we see some > inconsistencies during the switching process and some time after (when hinted > handnoff works). > > Basically I don't have any questions, just want to share our "ugly" failover > algorithm, to hear your criticism and may be advise on how to improve it. > Unfortunately we can't change replication factor and most of the time we have > to read with consistency level ONE (because we have strict requirements on > read performance). > > Thank you! >
