This really depends on your disks setup. When you run iostat under high load, do you see a high number of r/s but the rMB/s is not so great?
I usually use: iostat -x -m sdb sdc 1 to monitor situation like this. In my case my disk setup is the following: OS --> /sda Cassandra CommitLogs --> /sdb Cassandra Data --> /sdc My understanding is that during compaction cassandra does a lot of non sequential readsa then dumps the results with a big sequential write. Is your application mostly doing writes and little reads or the other way around. FR -----Original Message----- From: Yan Chunlu [mailto:springri...@gmail.com] Sent: Saturday, July 23, 2011 9:16 AM To: cassandra-u...@incubator.apache.org Subject: do I need to add more nodes? minor compaction eat all IO I have three nodes and RF=3, every time it is do minor compaction, the cpu load(8 core) get to >30, and iostat -x 2 shows utils is 100%, is that means I need more nodes? the total data size is <60G thanks! --
