> I understand that cassandra periodically cleans up the commitlog directories > by generating sstables in datadir. Is there any way to speed up this > movement from commitog to datadir?
commitlog_rotation_threshold_in_mb could cause problems if it was set very very high, but with the default of 128mb it should not be an issue. I suspect the most likely reason is that you have a column family whose memtable flush settings are extreme. A commit log segment cannot be removed until the corresponding data has been flushed to an sstable. For high-throughput memtables where you flush regularly this should happen often. For idle or almost idle memtables you may be waiting on the timeout criteria to trigger. So in general, having a memtable with a long expiry time will have the potential to generate commit logs of whatever size is implied by the write traffic during that periods. The memtable setting in question is the "memtable_flush_after" setting. Do you have that set to something very high on one of your column families? You can use "describe keyspace name_of_keyspace" in cassandra-cli to check current settings. -- / Peter Schuller
