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From Jay Svc <>
Subject Insert v/s Update performance
Date Tue, 26 Mar 2013 23:05:57 GMT
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.


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