You do want to spread your paging over as many LCU's as possible for performance reasons, but those can all be on the same DS8000. The one box really can act like more than one controller.
And rare, well, if it was, then why would you pprc mirror anyway? (locally that is :). We're not allowed to have any rares and unlikelys anyway. Also, if you are that concerned with availability you probably buy an adequate amount of memory to keep paging from being your bottleneck (at least in production). Marcy "This message may contain confidential and/or privileged information. If you are not the addressee or authorized to receive this for the addressee, you must not use, copy, disclose, or take any action based on this message or any information herein. If you have received this message in error, please advise the sender immediately by reply e-mail and delete this message. Thank you for your cooperation." -----Original Message----- From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Barton Robinson Sent: Tuesday, September 01, 2009 7:17 AM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: [IBMVM] Reaction of z/VM when losing a page dataset The problem with putting all your paging volumes on one DS-8000 then becomes performance. Your paging devices will now be sharing physical disks. When you write pages out to multiple "page devices", then all of the I/O is then going to the same set of hardware. From a performance perspective, you want to alternate page devices across ranks of physical devices. It is rare that you will lose the DS-8000. If you do, there are a lot of other things to worry about. Would be less optimal to have bad paging performance because of worrying about an outage that is very unlikely to happen. Florian wrote: > Thank you, > > This is what I expected. I fear also that the chance is doubled to crash the > system when the PAGING volumes are spread on both DS-8000. So I will correct > this soon. > >
