Do you have Reed Mullen's presentation? I can't remember where I saw it last, but it covers the different flavors of virtualization. There was also another at SHARE in Aug that compared/contrasted the various kinds of virtualizatoin.
Marcy Cortes Team Lead, Enterprise Virtualization - z/VM and z/Linux Enterprise Hosting Services w. (415) 243-6343 c. (415) 517-0895 "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:[EMAIL PROTECTED] On Behalf Of Alan Ackerman Sent: Friday, October 31, 2008 11:03 PM To: [email protected] Subject: Re: [IBMVM] I/O Overhead - z/VM versus VMWARE On Fri, 31 Oct 2008 11:37:40 -0400, Alan Altmark <[EMAIL PROTECTED] > wrote: >On Thursday, 10/30/2008 at 10:29 EDT, David Kreuter While I will grant >you the "optimization" point, let's not get too carri= ed >away. In an LPAR, SIE handles guest I/O only for dedicated OSA and FCP >adapters. All other I/O is virtualized by CP. SIE *does* handle CP's >I/O! > >The emphasis on the use of a virtual switch rather than dedicated OSAs >leaves us with primarily FCP adapters for SCSI. > >But with all that said, as others have pointed out, the word "overhead" >has no meaning. Yes, there is overhead and sometimes, yes, it can be >"n= ot >insignificant". The question is whether the applications are meeting >their SLAs and whether the IT provider is meeting its expense goals. >"C= an >I get acceptable application performance at a cost I can afford?" As >wa= s >mentioned, you may have more overhead handling an I/O request, but if >yo= u >can satisfy it from MDC, it was time well-spent. Assuming, of course, >you've got the CPU available to handle the I/O request! > >Alan Altmark >z/VM Development >IBM Endicott >========================= ========================== ========== ============== The person who asked the question has been asked to review virtualization= options (VMWARE, p- series, and z/VM) and determine which workloads should go where. Since th= midrange folks have so far decided "we don't need z/VM, we have VMWARE", this is actually pro= gress. Unfortunately, his background is all in PCs and Linux (and i-series), no = mainframe. But he really is trying to understand the mainframe. He wants to know if VM is like the VM= WARE he is failiar with - - at least he ASKED instaed of making assumptions. I don't think that the word "overhead" has no meaning. I'm pretty sure he= meant CPU overhead comparing native to a guest. I think that he has observed or been told th= at running Linux guests under VMWARE takes more processor than without VMWARE, and that this incr= eases for heavy I/O workloads. I would expect the same thing to be true for z/VM, but I would HOPE that = the mainframe does it better. Almost all I/O on a PC is handled by the central processors, whil= e the mainframe has the IOPs to do much of that work. It would be nice to quantify this, though. Alan Ackerman Alan (dot) Ackerman (at) Bank of America (dot) com
