Thanks Dean, I have used LCS with sstable_size_in_mb of 15. I have also tried bigger sstable_size_in_mb and observed simillar behavior.
Does compaction works differently for update v/s Insert? I belive all keys goes to single SST. What other options I should look into? Thanks, Jay On Tue, Mar 26, 2013 at 6:18 PM, Hiller, Dean <dean.hil...@nrel.gov> wrote: > Most likely compaction kicks in as updates cause duplicated rows in STCS > and compaction causes load that may not have been there before(check your > logs). Also, you can increase the number of nodes in your cluster as well > to better handle the load. > > Later, > Dean > > From: Jay Svc <jaytechg...@gmail.com<mailto:jaytechg...@gmail.com>> > Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" < > user@cassandra.apache.org<mailto:user@cassandra.apache.org>> > Date: Tuesday, March 26, 2013 5:05 PM > To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" < > user@cassandra.apache.org<mailto:user@cassandra.apache.org>> > Subject: Insert v/s Update performance > > Hi Team, > > I have this 3 node cluster. I am writing data to these node at the rate of > 2,000 records/second. What I observed that if I do inserts. (Means records > for those keys does not exist, my column family has 0 records to start > with) then I have better write performacne, low SSTable count, low pending > compaction and write latency is acceptable and CPU utilization on each node > between 35% to 85%. > > When I ran same test but for update this time (means records already > exists in Column family with same key), I observed that my SSTable count > gone high 3 times. Pending compactions gone high more than 2 times and > write latency has gone high too and CPU utilization was almost 92% to 100%. > > What is a reason of deteriorating Update performance v/s Insert > performance. Since this is critical you help is highly appriciated. > > P.S. I also observed that high number of pending Mutation Stage on my > nodetool tpstats. > > Thanks, > Jay >
