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From aaron morton <>
Subject Re: cassandra massive write perfomance problem
Date Thu, 21 Jul 2011 10:52:12 GMT

Without more info my initial guess is some GC pressure and/or IO pressure from compaction.
Check the logs for messages from the GCInspector or connect JConsole to the instance and take
a look at the heap. Here is some info on looking at the IO stats
With regard to the 25+GB on disk, that all depends on how much data you are writing. Be aware
that compacted files are not immediately deleted

You may also want to track things by looking at nodetool tpstats and cfstats (for latency).

Aaron Morton
Freelance Cassandra Developer

On 21 Jul 2011, at 21:49, lebron james wrote:

> Please help me solve one problem I have server with 4 GB RAM and 2x 4 cores CPU When
i start do massive writes in cassandra all works fine. but after couple hours with 10K inserts
per second database grows up to 25+ GB performance go down to 500 insert per seconds I find
out this because compacting operations is very slow and i dont understand why, i set 8 concurrent
compacting threads but cassandra dont use 8 threads only 2 cores are loaded.

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