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: IBMVM@LISTSERV.UARK.EDU 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
