Mark, Very nice, informative, post.
Harley Linker Jr. -----Original Message----- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Mark Post Sent: Monday, September 28, 2015 3:39 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: Documentation for Linux on z Systems and KVM - new >>> On 9/28/2015 at 02:25 AM, Sergey Korzhevsky <s_korzhev...@iba.by> wrote: > Alan Altmark wrote: >>> What is it about z that makes virtualization work better? >>50 years of work on it? > > That is interesting answer. One thing came to my mind is the live > guest relocation. As far as i could find, VMware introduced that > feature > (vMotion) in 2003, z/VM - in 2011. The same regarding network > (GuestLAN/VSwitch). > So, looks like z/VM slept all that years and was wake up by x86 world > recently. Having been an active participant and observer of the community for a while now, I think I can contribute some perspective. (From what I can tell, you have been also so I find your comment a little surprising.) When Linux for the mainframe was first introduced, a lot of facilities we take for granted today didn't exist. Guest LANs, VSWITCHes, cooperative memory management and so on. That started to change pretty quickly. Things that actually helped running more than just a few instances of Linux were introduced and made life much easier. Live Guest Relocation wasn't needed then, because not many shops were running huge amounts of guests. That pain came along later. Even then, it wasn't for the same reason that the x86 world wanted it. Mainframe shops running Linux on z/VM didn't worry much about hardware failures and migrating workload to relieve overloaded servers usually wasn't an issue because of decades of performance and capacity management. What "we" wanted it for was because z/VM was so reliable it could run for years but sometimes various maintenance was important to put on the system. Trying to get multiple customers of the service to agree on a maintenance window was becoming nearly impossible, because although they wanted High Availability, they weren't willing to actually invest in it, so the workload couldn't be failed over to another server in a cluster. There was another factor, although not a technical one. Many customers have become checklist driven. If your product doesn't allow them to put check marks in all the boxes on the list, it's obviously not a good product and not worthy of consideration. So, z/VM development was getting reports from Sales that this function was needed, just to be "in the game." And, being the group that they are, z/VM development wanted to approach the development needed in a more "system of systems" oriented way than just bolting on a feature. Thus, Single System Image was born, and it took quite a while and a lot of people to bring to the market. Taking into account the various diversions that were forced on them during the same period of time, it's amazing they got it out as quickly as they did. I think most people that have been in the z/VM world for a long time would agree that having Linux available on the mainframe has breathed new life into z/VM. Since then, they've been working hard to introduce things that make sense for the mainframe environment. What new items they work on, and what priority they have, _can_ be influenced by current and potential customers. I encourage anyone who has thoughts on what those new items should be to speak up, whether here or in the IBMVM mailing list, or at SHARE. There are people in these mailing lists and at SHARE that have a direct line into the z/VM and Linux development groups at IBM. Take advantage of that. Mark Post ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/ *************************************************************************** The information contained in this communication is confidential, is intended only for the use of the recipient named above, and may be legally privileged. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. 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