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From Jeremiah Jordan <jeremiah.jor...@morningstar.com>
Subject Re: commit log size
Date Mon, 28 Nov 2011 19:53:59 GMT
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.

-Jeremiah

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!
>
> Thanks,
> Alex

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