[sheepdog-users] cache performance test

[Liu Yuan]

On Wed, Jun 26, 2013 at 12:12:59PM +1000, Joseph Glanville wrote:
> Deadline is good but on faster systems you are better off with noop.
> Especially if there is a RAID card or SSDs involved.

noop does only back merge and just throw requests to driver's request queue blindly.
Deadline will do following for you
- separate read/write request and batch requests
- priority read request over write one
- aggressive request merge

So it depends on how intelligence your SSD is. Basically, if you use a ordinary SSD
like Samsung 840 Pro, you'd better choose deadline because its internal request queue
depth is kind of short. If you use a much powerful SSD like fusionio, use noop instead
because any software request handling is considered bottleneck for it.

Thanks,
Yuan