I forget to mention I am using C* 2.2.4 On Jan 15, 2016 3:53 PM, "Kai Wang" <dep...@gmail.com> wrote:
> 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. >
