On Wed, Jul 21, 2010 at 1:30 PM, Juho Mäkinen <juho.maki...@gmail.com> wrote: > I'm just about to extend my current two node production cluster into > five node cluster and I'd like to be sure that my plan is correct. > > Currently cluster has two nodes with RF=2. The target is to add four > nodes, increase RF to 3 and drop one of the old nodes. > > My current plan is: > 1) Add one node with RF=3 but keep the clients connecting only to the > two old nodes. As I'm doing many reads with ConsistencyLevel.ONE, this > should prevent the clients getting exceptions about missing keys. > > 2) Restart both old nodes with configuration that has RF=3. The > following inserts should now be propagated to the new 3rd node.
At this point, CL.ONE reads to the old nodes will return no data for 1/3 of the reads (because they incorrectly believe that they have a copy of all the data locally). > 7) Execute "nodetool loadbalance" to nodes if needed. It will be less painful (in terms of I/O and CPU consumed) to calculate the right locations ahead of time and bring up the new nodes with the appropriate InitialToken specified. > I'm also thinking about the possibility to add one node to another > data center which would act as a live backup node. The idea would be > that all keys should have a copy in the backup machine. If I'm > correct, this can be done with RackAwareStrategy as stated in > Operation wiki page. RackAwareStrategy will put a copy of *each* key in both datacenters. Usually this is problematic if one DC has much less machines than the other. -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of Riptano, the source for professional Cassandra support http://riptano.com
