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From Benjamin>
Subject Re: 0.7 memory usage problem
Date Sun, 26 Sep 2010 02:53:01 GMT
The log posted shows _10_ pending in MPF stage, and the errors show
repeated failures trying to flush memtables at all:

 INFO [GC inspection] 2010-09-24 13:16:11,281 (line
156) MEMTABLE-POST-FLUSHER             1        10

You are also flushing _really_ small memtables to disk (looks to be
triggered by the default ops threshold):

 INFO [FLUSH-WRITER-POOL:1] 2010-09-24 12:55:27,296
(line 150) Writing Memtable-HiFreq@741540175(15105576 bytes, 314640

Based on what you said initially:

"600 row (60 columns per row) per second, ~3K size rows"

If that is so, you are writing 36000 columns per second to a single
machine (why are you not distributing the client load across the
cluster, as is best practice?).  If your RF is 3 on your 3 node
cluster, every node is taking every write, so you are trying to
maintain 36000 writes per second per node.  Even with a dedicated
(spinning media) commitlog drive, you can't possibly keep up with

What is your disk setup?

What CL are you using for these writes?

Can you post your client code for doing the writes?

It is odd that you are able to do 36000/sec _at all_ unless you are
using CL.ZERO, which would quickly lead to OOM.


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