> Thanks to all for replying, but frankly I didn't get the answer I wanted. > Does the "number of disks" apply to number of spindles in RAID0? Or > something else like a separate disk for commitlog and for data?
The number of actual disks (spindles) in the device on which your sstables are on (not the commit log). The reason for this is that you want to be able to saturate your storage subsystem, and that means keeping all spindles working at all times and efficiently. This is accomplished by ensuring you are able to sustain a sufficient queue depth (number of outstanding commands) on each device. This in turn, in the case of a RAID0, means multiplying the target maximum queue depth with the number of drives. -- / Peter Schuller
