On Wednesday, 06/20/2007 at 06:32 MST, "O'Brien, Dennis L" <Dennis.L.O'[EMAIL PROTECTED]> wrote: > In the recent "dasd 3390 -27" thread, Kris Buelens said, "For SFS though > (and probably DB2) PAV is maybe of limited help: a given SFS server will > start only one I/O to all its minidisks on the same disk." Is that > really true? Does an SFS server look at the real devices or volsers > that its minidisks are on, and only start an I/O to one minidisk on a > volume at a time?
That is incorrect. SFS performs overlapping I/O using the *BLOCKIO system service. SFS does make some attempt to not overload a single real disk volume. If he can, SFS will try to limit the number of I/Os outstanding on a single *real* volume, rotating to minidisks on other volumes in the storage group that are on different real volumes. CP (*BLOCKIO) will only use a PAV if he starts to build an I/O queue. If there's nothing in queue, CP won't use a PAV. As others have said, PAV only buys you something if you have a problem it can solve (I/O queuing). Alan Altmark z/VM Development IBM Endicott
