> I don't understand why I > don't get multiple concurrent compactions running, that's what would > make the biggest performance difference. concurrent_compactors Controls how many concurrent compactions to run, by default it's the number of cores on the machine.
If you are not CPU bound check iostats (http://spyced.blogspot.co.nz/2010/01/linux-performance-basics.html_) Cheers ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 12/03/2012, at 7:21 PM, Thorsten von Eicken wrote: > On 3/11/2012 9:17 PM, Peter Schuller wrote: >>> multithreaded_compaction: false >> Set to true. > I did try that. I didn't see it go any faster. The cpu load was lower, > which I assumed meant fewer bytes/sec being compressed > (SnappyCompressor). I didn't see multiple compactions in parallel. > Nodetool compactionstats behaved strange and instead of showing > individual compactions with a %-complete it showed a running count of > total bytes compacted. (Darn, I don't have the output of that anymore in > my terminal buffer.) It just didn't look good to me. Are you positive > that it is faster with leveled compaction? I don't understand why I > don't get multiple concurrent compactions running, that's what would > make the biggest performance difference. Is the compaction parallelism > perhaps only across multiple CFs? That would explain what I see. > > Thorsten
