I tried the following : - always one cassandra node on one EC2 m.large instance. two other m.large instance, I run 4 stress.py (50 thread each, 2 stress.py on each instance) - RAID0 EBS for data and ephemeral EBS (/dev/sda1 partition) for commit log. - -Xmx4G
and I did not see any improvements (Cassandra stays around 7000 W/sec). CPU is running up to 130% (spike) but I have two 2,5Ghz CPU the avgqu-sz goes up to 20 (sometimes more) (for the device /dev/sda1 that stores the commitlog) Do you think concurrentWrites or MemtableThroughputInMB parameters must be increased (using default value right now) Any suggestions are welcomed. ;o) On Fri, Jun 18, 2010 at 7:42 PM, Benjamin Black <b...@b3k.us> wrote: > On Fri, Jun 18, 2010 at 8:00 AM, Olivier Mallassi <omalla...@octo.com> > wrote: > > I use the default conf settings (Xmx 1G, concurrentwrite 32...) except > for > > commitlog and DataFileDirectory : I have a raid0 EBS for commit log and > > another raid0 EBS for data. > > I can't get through 7500 write/sec (when launching 4 stress.py in the > same > > time). > > Moreover I can see some pending tasks in the > > org.cassandra.db.ColumnFamilyStores.Keyspace1.Standard1 MBean > > Any ideas on the bottleneck? > > Your instance has 7.5G of RAM, but you are limiting Cassandra to 1G. > Increase -Xmx to 4G for a start. You are likely to get significantly > better performance with the ephemeral drive, as well. I suggest > testing with commitlog on the ephemeral drive for comparison. > > > b > -- ............................................................ Olivier Mallassi OCTO Technology ............................................................ 50, Avenue des Champs-Elysées 75008 Paris Mobile: (33) 6 28 70 26 61 Tél: (33) 1 58 56 10 00 Fax: (33) 1 58 56 10 01 http://www.octo.com Octo Talks! http://blog.octo.com
