> ok, so we just lost the data on that node. are building the raid on it, but > once it is up what is the best way to bring it back in the cluster
You're saying the raid failed and data is gone? > just let it come up and run nodetool repair > copy data from another node and then run nodetool repair, > > do I still need to run repair immeidately if I copy the data? Want to > schedule repair for later during non peak hours? If data is gone, the safe way is to have it re-join the cluster: http://wiki.apache.org/cassandra/Operations#Handling_failure But note that in your case, since you've lost data (if I understand you), it's effectively a completely new node. That means you either want to switch it's IP address and go for the "recommended" approach, or do the other option but that WILL mean the node is serving reads with incorrect data, violating the consistency. Depending on your application, this may or may not be the case. Unless it's a major problem for you, I suggest bringing it back in with a new IP address and make it be treated like a completely fresh replacement node. Probably decreases the risk of mistakes happening. As for the other stuff about repair in the e-mail you pasted; periodic repairs are part of regular cluster maintenance. See: http://wiki.apache.org/cassandra/Operations#Frequency_of_nodetool_repair -- / Peter Schuller (@scode on twitter)
