The IBM z/VM Operating System <IBMVM@LISTSERV.UARK.EDU> wrote on 02/19/2008 04:53:22 PM:
> Given that performance is very nearly the same between SAN and EDEV > connections, or acceptably so, then I would recommend that you go with > the EDEV approach. Just have your SAN folks carve out a big chunk of SAN > storage for your use, and then allocate EDEV (FBA type) disk storage for > guests as needed from that large pool. You want to minimize your > contacts with the SAN folks, I think. > > Good luck. > I don't think the performance is very close. Here's some anecdotal evidence... For Danu (z9) GA 3, we (firmware) were roped into measuring the FBA performance difference: GA 2 vs GA 3. We wanted to determine if firmware changes that helped direct attached IOs/sec also helped FBA. The testing procedure was ad hoc. We found a configuration of FBA devices that would get the max 4k SCSI reads/sec from 1 channel. We got numbers with the GA 2 firmware. We upgraded the FCP firmware to GA 3, and used the same FBA config to get a new set of numbers. We then compared to direct attached 4k SCSI reads/sec numbers that we already had. Direct attached was something like 50% faster for both levels of firmware. Sorry that I don't have more details, but it was over a year ago, and I no longer have the string of notes. If anyone out there is contemplating FBA vs direct attached and performance is a concern, I think you should do some of your own tests before deciding. Ray Higgs System z FCP Development Bld. 706, B24 2455 South Road Poughkeepsie, NY 12601 (845) 435-8666, T/L 295-8666 [EMAIL PROTECTED]
