(not answering (1) right now, because it's more involved) > 2. Does a Nodetool Repair block any reads and writes on the node, > while the repair is going on ? During repair, if I try to do an > insert, will the insert wait for repair to complete first ?
It doesn't imply any blocking. It's roughly similar to compaction in its impact on nodes; in addition when data is streamed (if any) the impact should be similar to node bootstrapping. > 3. I read that repair can impact your workload as it causes additional > disk and cpu activity. But any details of the impact mechanism and any > ballpark on how much the read/write performance deteriorates ? The compaction part will have an impact similar to regular compaction except it's read-only (no writing of new sstables). It is subject to compaction throttling if you run a version of Cassandra with compaction throttling. Streaming causes disk/networking load and is not yet rate limited like compaction. In addition be aware that repair can cause disk space usage to temporarily increase if there are significant differences to be repaired. -- / Peter Schuller
