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From aaron morton <aa...@thelastpickle.com>
Subject Re: cassandra massive write perfomance problem
Date Thu, 21 Jul 2011 10:52:12 GMT
background http://wiki.apache.org/cassandra/FAQ#slows_down_after_lotso_inserts

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 http://spyced.blogspot.com/2010/01/linux-performance-basics.html
 
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 http://wiki.apache.org/cassandra/FAQ#cleaning_compacted_tables

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

Cheers
  
-----------------
Aaron Morton
Freelance Cassandra Developer
@aaronmorton
http://www.thelastpickle.com

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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