On Thu, Mar 4, 2010 at 6:21 PM, George Henke <gahe...@gmail.com> wrote: >However, it still "begs the question", why have LPARs at all, because >separate Security DBs *can* be configured in separate Virtual Machines
Even with VM, there are cases where the complete isolation of LPARs is useful for testing system software (separate, real IOCP, etc.,; virtual LANs have helped a lot here). But you seem to be saying, "Why use LPAR instead of z/VM?" In general, z/OS shops prefer the control offered by LPAR. As a long-time VMer, I see that as heresy, but I do understand the underlying argument that says "I don't have to administer PR/SM the same way I have to administer z/VM". Add to that the fact that all machines are LPAR-Mode-only now, plus the cost of z/VM, and it's a no-brainer for many. ObAnecdote: back at Linuxcare, we had a Multiprise 3000 with 2 IFLs (yeah, the only one in the world, probably -- IBM gave us a special dispensation to have 2 IFLs instead of requiring a CP). We had 4 VM LPARs on it: one DIRMAINT, one VM:Secure, one native directory handling, one for demos. And of course a boatload of Linux guests on each VM. I said, "This is dumb. We have VM; we should run in Basic Mode with four VM guests and it will be better, because we'll share real memory, both processors, etc. (the demo LPAR was largely idle, as well). So we tried it. It was horrible -- on the order of 10x slower. But we had no tools to measure it and no time to fool with it, so we went back to LPAR-mode. I still wonder why it was so bad! ...phsiii ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
