Jonathan, Are you sure that the reads done for compaction are sequential with Cassandra 0.6.13? This is not what I am observing right now. During a minor compaction I usually observe ~ 1500 to 1900 r/s while rMB/s is barely around 30 to 35MB/s.
Just asking out of curiosity. FR -----Original Message----- From: Jonathan Ellis [mailto:jbel...@gmail.com] Sent: Saturday, July 23, 2011 5:05 PM To: user@cassandra.apache.org Subject: Re: do I need to add more nodes? minor compaction eat all IO On Sat, Jul 23, 2011 at 4:16 PM, Francois Richard <frich...@xobni.com> wrote: > My understanding is that during compaction cassandra does a lot of non > sequential readsa then dumps the results with a big sequential write. Compaction reads and writes are both sequential, and 0.8 allows setting a MB/s to cap compaction at. As to the original question "do I need to add more machines" I'd say that depends more on whether your application's SLA is met, than what % io util spikes to. -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of DataStax, the source for professional Cassandra support http://www.datastax.com
