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From Jay Svc <jaytechg...@gmail.com>
Subject Re: Insert v/s Update performance
Date Wed, 27 Mar 2013 00:08:52 GMT
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.Hiller@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 <jaytechgeek@gmail.com<mailto:jaytechgeek@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
>

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