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From Alexandru Dan Sicoe <>
Subject commit log size
Date Mon, 28 Nov 2011 17:11:02 GMT
Hello everyone,

4 node Cassandra 0.8.5 cluster with RF=2, replica placement strategy =
SimpleStartegy, write consistency level = ANY, memtable_flush_after_mins
=1440; memtable_operations_in_millions=0.1; memtable_throughput_in_mb = 40;
max_compaction_threshold =32; min_compaction_threshold =4;

I have one keyspace with 1 CF for all the data and 3 other small CFs for
metadata. I am using Datastax OpsCenter to monitor my cluster so there is
another keyspace for monitoring.

Everything works ok, the only thing I've noticed is this morning the
commitlog of one node was 52GB, one was 25 GB and the others were around 3
GB. I left everything untouched and looked a couple of hours later and the
52GB one is now about 3GB and the 25 GB one is now 29 GB and the other two
about the same as before.

Are my commit logs growing because of small memtables which don't get
flushed because they don't reach the operations and throughput limits? Then
why do only some nodes exhibit this behaviour?

It would be interesting to understand how to control the size of the
commitlog also to know how to size my commitlog disks!


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