Ok, thanks!

On Mon, Nov 28, 2011 at 8:53 PM, Jeremiah Jordan <jeremiah.jordan@morningstar.com> wrote:
Yes, the low volume memtables are causing the problem.  Lower the thresholds for those tables if you don't want the commit logs to go crazy.


On 11/28/2011 11:11 AM, Alexandru Dan Sicoe wrote:
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!


Alexandru Dan Sicoe
MEng, CERN Marie Curie ACEOLE Fellow