storage given to ZOS guests

[Jim Bohnsack]

Duane--My experience in running multiple guest MVS systems is to give them
a virtual size such that their working sets will generally fit in storage
causing the MVS system itself to manage and do it's own paging. One thing
that you absolutely do not want to happen to a production guest is to have
it not be dispatchable because of a page fault. MVS is good at
paging. Let it page. You'll have to experiment to find the optimum
size. Use the Perf. Toolkit or ESAMON or something like that.

Jim

At 03:49 PM 2/6/2006, you wrote:
>I have a VM system that is going to host 2-3 ZOS guest systems running at
>the same time.
>
>The z/VM system is running the default service machines, including TCPIP
>and FTPSERVE.
>
>The VM system itself has a total of 3152m of storage.
>
>How does one determine how much storage can be given to one or more zOS
>guests?
>
>
>Duane
>Ohio State U.

Jim Bohnsack
Cornell Univ.
[phone]

[David Kreuter]

Duane: It depends (sic) on what your expectations are concerning storage residency. Prior to z/VM 5.2 you can use preferred guest storage (V=R or V=F) whereby all the storage of 1 or more z/os guests can be permanently assigned in memory. At this point it a counting calculation game for your z/OS guests. CP will happily page non-preferred guest memory of any virtual machine.

In z/VM 5.2 preferred guest storage is not available. You can LOCK the pages of your z/OS guest; you'll have to know which pages to lock! You can try and lock all. Locking all pages of machines guarantees those pages are always in memory. Page locking does not have the same benefits of preferred storage. Preferred guest support (of which storage is part of) provides extensive I/O benefits as well.

Or you can let CP happily page memory for all machines including your z/OS machines then decide on your course of actions based on response time or lack thereof. Over time LRU pages will be moved out of main memory including those for the z/OS guests.
David


-----Original Message-----
From: VM/ESA and z/VM Discussions on behalf of Duane Weaver
Sent: Mon 2/6/2006 3:49 PM
To: VMESA-***@LISTSERV.UARK.EDU
Subject: storage given to ZOS guests

I have a VM system that is going to host 2-3 ZOS guest systems
running at the same time.

The z/VM system is running the default service machines, including
TCPIP and FTPSERVE.

The VM system itself has a total of 3152m of storage.

How does one determine how much storage can be given to one or more zOS guests?


Duane
Ohio State U.