Well ... for me ... it's not an issue of what benefit having a PAV alias(es) for a given volume might yield. It's a question of support and toleration (for example, will VM:Backup or HiDRO back the BASE up and erroneously back the potential PAV alias(es) too?).
So, up until recently (6 months ago or so [we did a huge DASD migration]), each time our storage group got a new disk array (IBM or Hitachi, whatever), they would hard-code PAV alias addresses into the "DASD subsystem" ... because z/OS needed that. When this was done, z/VM 5.3 could "see and use" the PAV alias(es) (for non-z/OS volumes too). However, now, z/OS does not require that PAV alias(es) be defined to the disk array (hard coded in the DASD subsystem) with the newer DASD subsystems ... z/OS (I think via WLM) can *dynamically define* PAV aliases to alleviate I/O contention ... the PAV aliases do not need to be pre-defined or hard-coded in the DASD subsystem/configuration. (This is why our storage group no longer defines the PAV alias addresses to the DASD subsystem ... and won't for z/VM.) Please correct me if I'm wrong, but z/VM still requires the PAV alias(es) to be hard-coded/pre-defined to the DASD subsystem ... HyperPAV support or whatever in z/VM. Otherwise, z/VM can not support PAV aliases. This is what we've experienced at our site. If there's something we are missing in the z/VM support, please let me know. Thanks, JR JR (Steven) Imler CA Senior Software Engineer Tel: +1 703 708 3479 Fax: +1 703 708 3267 [EMAIL PROTECTED] > -----Original Message----- > From: The IBM z/VM Operating System > [mailto:[EMAIL PROTECTED] On Behalf Of Bill Bitner > Sent: Thursday, July 03, 2008 04:52 PM > To: IBMVM@LISTSERV.UARK.EDU > Subject: Re: z/VM 5.3 and PAV > > Are you concerned you'll need PAV as you consolidate current > volumes? or as you grow current workloads? If the former, I'd > suggest looking at some statistics like I/O rate per GB of > disk storage. For example if you are doing 15 I/Os a second on > a 2.7GB disk, that's 5.6 I/Os/GB. If you are then going to > configure your new volumes as 24GB volumes then on average > you'd have 134.4 I/Os per second for the volumes. Ask your > vendor about whether that would be significant enough to > warrant PAV. It's been my experience that most VM shops do > not need PAV for large number of volumes in the same way > as they do in z/OS shops. If you do need PAV, a couple > sources of additional information include: > http://www.vm.ibm.com/storman/pav/index.html > http://www.vm.ibm.com/devpages/farman/WAVVPAV.PDF > http://www.vm.ibm.com/perf/reports/zvm/html/530hpav.html > http://www.vm.ibm.com/perf/reports/zvm/html/520pav.html > > Bill Bitner > >
