I have recently tested this scenario under a couple versions of Cassandra and have been able to write and read to/from the cluster while performing a move.
I performed these tests utilizing an RF=2 on a three node cluster while performing quorum reads and received no errors due to unavailable replicas. I will be doing some more testing on this under different scenarios, but so far so good However, I would strongly recommend an RF of at least 3 when performing quorum based reads because otherwise you're subject to failed reads in event of losing one node. -- Colin 320-221-9531 > On Apr 16, 2014, at 6:28 PM, Richard Low <rich...@wentnet.com> wrote: > >> On 16 April 2014 05:08, Jonathan Lacefield <jlacefi...@datastax.com> wrote: >> Assuming you have enough nodes not undergoing "move" to meet your CL >> requirements, then yes, your cluster will still accept reads and writes. >> However, it's always good to test this before doing it in production to >> ensure your cluster and app will function as designed. > > This is not a correctness requirement: writes go to the move source and > destination during the move and reads come from the source. Otherwise you > could lose data during move (and certainly would lose data if replication > factor was one). However, nodes that are involved in the move will be slower > so it will be better for performance to not move nodes that share replicas > simultaneously. > > Richard.
