Thanks Maki and Tyler. Re: Q1: I think its the time for me to think about LevelCompaction at this time. But I'm happy to know I can run major compactions as often as I like if I can afford.
Re: Q2: Other than the high IO impact if there won't be any data corruption/consistency issues I think I can afford this too. Thanks, Eran Chinthaka Withana On Wed, Feb 29, 2012 at 7:17 PM, Tyler Hobbs <ty...@datastax.com> wrote: > At this point, using LeveledCompaction is a much better way to have good > guarantees about how many sstables your reads will hit (and thus better > latency guarantees) than SizeTiered with periodic major compactions. > > > On Wed, Feb 29, 2012 at 8:49 PM, Maki Watanabe <watanabe.m...@gmail.com>wrote: > >> DataStax has not recommend to run major compaction now: >> http://www.datastax.com/docs/1.0/operations/tuning >> But if you can afford it, major compaction will improve read latency as >> you see. >> >> Major compaction is expensive, so you will not want to run it during >> high traffic hours. And you should not run it more than 1 node in >> replicas same time. You should not run repair and major compaction in >> same time in same (affected) node, because both of the tasks require >> massive io. >> With these constraints, as often as you run major compaction, you will >> get better read latency. >> >> 2012/3/1 Eran Chinthaka Withana <eran.chinth...@gmail.com>: >> > Hi, >> > >> > I have two questions on major compactions (the ones user initiate using >> > nodetool) and I really appreciate if someone can help. >> > >> > 1. I've noticed that when I run compactions the read latency improves >> even >> > more than I expected (which is good :) ) The improvement is so tempting >> that >> > I'd like to run this almost every week :). I understand after a >> compaction >> > Cassandra will create one giant SSTable and if something happens to it >> > things can go little bit crazy. So from your experience how often >> should we >> > be running compactions? What parameters will influence this frequency? >> > >> > 2. I'm thinking scheduling compactions using a cron job. But the issue >> is I >> > scheduled repairs also using a cronjob to run once in GC Period (of >> default >> > 10 days). Now the obvious question is what will happen if a node is >> running >> > both the compactions AND the repair at the same time? Is this something >> we >> > should avoid at all costs? What will be the implications? >> > >> > Thanks, >> > Eran Chinthaka Withana >> > >> >> >> >> -- >> w3m >> > > > > -- > Tyler Hobbs > DataStax <http://datastax.com/> > >
