VDISK is different. Actually, it isn't vdisk is different, it is memory is different.
CP lets me throttle every other shared resource. I can SET SHARE to throttle or cap CPU. I can throttle or cap I/O rates for a particular user. But once I give a user access to virtual storage (max guest machine size plus vdisk(s)), I can't throttle his usage. And in the very vast amount of cases, I wouldn't want to. But if/when that time comes, when vdisk starts getting pounded, in effect the working storage size of that guest, jumps to something you never seen before, or expected, and even when planned for, impacts the production systems (as they start getting paged out). Well behaved systems, Linux or otherwise, are not a problem. Test and development systems, by their nature, may go grab memory and keep going. All of a sudden, the working set for that machine might double/triple, and CP will do its best to accommodate. And it does so, not by paging out the offending machines pages, but by paging out other machines pages. The offending machines pages are the most recently used pages and will stay in storage. We don't have a "set maxressize=" parm in CP. Tom Duerbusch THD Consulting >>> [EMAIL PROTECTED] 2/24/2007 9:48 AM >>> >>> On Sat, Feb 24, 2007 at 10:36 AM, in message <[EMAIL PROTECTED]>, Tom Duerbusch <[EMAIL PROTECTED]> wrote: -snip- > One of the origional posts was on the pros and cons of vdisk. No one > brought up that it is a shared resource, in a shared environment. > Anytime you abuse a shared resource, it will cause performance problems > with all other guests. Vdisk isn't free or worry free. That is the > jist of the discussion from my point of view. The whole point of z/VM is sharing resources. Explain how VDISK is any different from the rest of them. The systems programmer has absolute control over how resources are shared. If bad things happen because a guest actually uses what it was granted, the problem lies not with the fact that the guest used it, but with the systems programmer. Mark Post ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
