best way to run nodetool upgradesstables after update?

Question

I'm currently in the process of upgrading a 21 node cluster from 0.8 to version 1.0.11. The cassandra upgrade process requires that sstables are updated to the latest format after an upgrade of the software (via nodetool upgradesstables). This process seems to take a very long time. I have one node that's been running it for 48 hours and still isn't done.

I would like to know if it's advisable to do this in parallel on all the nodes. Specifically, what would be the performance implications? This cluster is under fairly heavy r/w use and needs to be available 24/7.

Answer 1

During compaction, your nodes will be re-writing every sstable at the speed of "compaction_throughput_mb_per_sec".

My guess is that the performance implications are directly linked to the value of this setting. A low value (default is 16Mb, you can go lower) should allow you to upgrade your cluster without slowing it down.