Hi, I am trying to figure out the bottleneck of compaction on my node. The node is CentOS 7 and has SSDs installed. The table is configured to use LCS. Here is my compaction related configs in cassandra.yaml:
compaction_throughput_mb_per_sec: 160 concurrent_compactors: 4 I insert about 10G of data and start observing compaction. *nodetool compaction* shows most of time there is one compaction. Sometimes there are 3-4 (I suppose this is controlled by concurrent_compactors). During the compaction, I see one CPU core is 100%. At that point, disk IO is about 20-25 M/s write which is much lower than the disk is capable of. Even when there are 4 compactions running, I see CPU go to +400% but disk IO is still at 20-25M/s write. I use *nodetool setcompactionthroughput 0* to disable the compaction throttle but don't see any difference. Does this mean compaction is CPU bound? If so 20M/s is kinda low. Is there anyway to improve the throughput? Thanks.
