On Thu, Feb 19, 2009 at 09:28:31PM +0200, Or Gerlitz wrote: > Sorry, but why file system over block device whose scheduler being > noop is a bad idea?
The noop scheduler doesn't re-order requests, so concurrent accesses to multiple files will cause lots of extra seeking and throughput collapses. The cfq and anticipatory schedulers will delay some I/O requests in order to increase the physical locality of sequences of requests. Deadline also does this to a lesser extent. Which is best really depends on your access patterns. If you mostly just do long sequences of reads or writes, noop generally wins because of its lower latency and minimal overhead. Even if there are multiple users of the filesystem, noop often isn't too bad because a lot of drives and HBAs do their own re-ordering behind the scenes. In my experience, noop works well on the initiator. On the target, deadline is slightly better than noop on the target for the workloads I see, on my equipment, YMMV. Regards, Mark. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to open-iscsi@googlegroups.com To unsubscribe from this group, send email to open-iscsi+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/open-iscsi -~----------~----~----~----~------~----~------~--~---
