http://www.datastax.com/dev/blog/when-to-use-leveled-compaction
"If you perform at least twice as many reads as you do writes, leveled compaction may actually save you disk I/O, despite consuming more I/O for compaction. This is especially true if your reads are fairly random and don’t focus on a single, hot dataset." From: Brian Tarbox <tar...@cabotresearch.com<mailto:tar...@cabotresearch.com>> Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> Date: Monday, January 7, 2013 12:56 PM To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> Subject: Re: help turning compaction..hours of run to get 0% compaction.... I have not specified leveled compaction so I guess I'm defaulting to size tiered? My data (in the column family causing the trouble) insert once, ready many, update-never. Brian On Mon, Jan 7, 2013 at 3:13 PM, Michael Kjellman <mkjell...@barracuda.com<mailto:mkjell...@barracuda.com>> wrote: Size tiered or leveled compaction? From: Brian Tarbox <tar...@cabotresearch.com<mailto:tar...@cabotresearch.com>> Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> Date: Monday, January 7, 2013 12:03 PM To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> Subject: help turning compaction..hours of run to get 0% compaction.... I have a column family where I'm doing 500 inserts/sec for 12 hours or so at time. At some point my performance falls off a cliff due to time spent doing compactions. I'm seeing row after row of logs saying that after 1 or 2 hours of compactiing it reduced to 100% of 99% of the original. I'm trying to understand what direction this data points me to in term of configuration change. a) increase my compaction_throughput_mb_per_sec because I'm falling behind (am I falling behind?) b) enable multi-threaded compaction? Any help is appreciated. Brian ---------------------------------- Join Barracuda Networks in the fight against hunger. To learn how you can help in your community, please visit: http://on.fb.me/UAdL4f Southfield Public School students safely access the tech tools they need on and off campus with the Barracuda Web Filter. Quick installation and easy to use- try the Barracuda Web Filter free for 30 days: http://on.fb.me/Vj6JBd
