One other facet to this discussion....cost On the z/890, the FICON adapters were $25K each. The FCP adapters were $25K each.
Then, you need the adapters on the storage unit. We went to an IBM DS6800. The Business Partner was somewhat pushing the FCP adapters for our growing Linux workload. The DS6800 would be LPARed into a FICON attached side for CKD data, and a FCP side for scsi attached access. I took one look at the cost and couldn't justify, at this time, FCP. We can always add it in the future. And I expect when we replace the z/890, FCP will be just one of those "standard" things. Yep, would still be optional, but everyone orders it. If we were pushing the I/O thru on the Linux side, perhaps running a second IFL, then the cost/performance issue would be moot. But right now, on my system, FCP doesn't resolve any issues. I would like to say that I have better uses for the $100k, but the real issue was the extra cost would sink the prospects for buying the z/890 and DS6800. Tom Duerbusch THD Consulting >>> [EMAIL PROTECTED] 3/16/2006 7:51 AM >>> Rob, IBM has published some numbers for FBA emulation on SCSI for Linux guests: "Linux Disk I/O Alternatives" at http://www.vm.ibm.com/perf/reports/zvm/html/520lxd.html it's clear there's a CPU overhead penalty for FBA emulation; but not clear if the pain would be noticeable. -------------------------------------------------------- This e-mail, including any attachments, may be confidential, privileged or otherwise legally protected. It is intended only for the addressee. If you received this e-mail in error or from someone who was not authorized to send it to you, do not disseminate, copy or otherwise use this e-mail or its attachments. Please notify the sender immediately by reply e-mail and delete the e-mail from your system. -----Original Message----- From: VM/ESA and z/VM Discussions [mailto:[EMAIL PROTECTED] On Behalf Of Rob van der Heij Sent: Thursday, March 16, 2006 3:31 AM To: [email protected] Subject: Re: DASD I/O performance VM 44 vs. VM 52 On 3/15/06, Romanowski, John (OFT) <[EMAIL PROTECTED]> wrote: > On VM 5.2 I'm considering trying FBA emulation on SCSI for Linux guests > to simplify each Linux guest's configuration and save staff time. > > If the additional CPU overhead doesn't hurt much it'll be worth it. I have no numbers from such a configuration (but would be interested to see them) so I cannot tell what the impact of this will be. I normally avoid to express an opinion about things I have not tried and measured myself. All I can tell is that the FBA emulation on SCSI was meant for shops that want their Linux data on SCSI to "simplify configuration and save staff time" ;-) because they have an investment in the "open storage" area. For those shops it would be a PITA to define S/390 I/O as well just to hold the basic VM system. Now if you would say that Open FCP for Linux on z/VM would greatly benefit from virtualizing that support on z/VM, then I could not agree more with you. In addition to connecting to and managing the Open FCP data, I could also see some fun in having a virtual SAN living on VM paging space. And I am sure that this is not the first time our friends in z/VM planning see this idea... Rob -- Rob van der Heij Velocity Software, Inc
