Hi, Brian.
A couple of things to consider that you didn't mention in your note:
1) what version of z/VM are you considering? There have been significant
changes in recent versions w.r.t. the z/OS guest support. E.g., z/VM 5.1
does not support preferred guest (V=R and V=F) virtual machines
2) Guest support for advanced z/OS functions like crypto hardware might
be something your site needs to consider as well.
Hope this is of some help. Good luck.
DJ
Brian Nielsen wrote:
We currently run z/OS in multiple LPARS, one for production, two for test,
with more LPARs for both production and test on the way. We also run a
z/VM LPAR on IFLs for LINUX guests.
I'm putting together a pros & cons list for running z/VM on the CP side
with some or all of the z/OS systems as guests. I'd like to make sure I
don't leave out anything important. There would be no other work in that
z/VM image other than the z/OS guests, so the main thrust is the improved
management of the z/OS images and devices. If the production LPARs are
under z/VM they would almost certainly have RESERVED pages to
minimize/eliminate them being paged by z/VM.
My high level outline has:
Cons:
- Additional license charges for z/VM on CP engines
- z/VM will use some CPU, memory, & DASD
- Some operating procedures will change
- z/OS Systems Programmers & Operators will need some z/VM skills
Pros:
- Virtualization allows better workload isolation and resource sharing
- Fewer POR's to make LPAR changes, and new guests on demand
- Some real CTC's & devices can be replaced by virtual counterparts
- VM minidisk support can be used to improve DASD management
- Can simulate the disaster recovery site
There are some items I don't know enough about yet to gauge the impact:
- Workload Manager is used to throttle back the z/OS LPARS below a
specified 4 hour rolling average of CPU usage (for cost reasons). I've
never used Workload Manager, but wonder: (a) will it work if z/OS is a
guest of z/VM, and (b) if not, what would accomplish the same thing?
Setting SHAREs is obviously not up to the task because we're talking about
the whole CP side.
- How do I properly evaluate if the production LPARs should be left alone
and to only consolidate the test LPARs under z/VM?
- How will SMF records from z/OS, which are used for billing, be impacted?
- What will the impact of the additional level of SIE on z/OS be?
Have I overlooked anything major? (Especially z/OS specific issues.)
I'm trying to anticipate questions so that I have answers and to avoid
surprises later.
When other people have made this type of change, what problems popped up?
What problems disappeared?
Many (many) years ago I used to run MVS under VM/SP on a 4381, so that
environment isn't new to me, it's just not recent vintage.
Thanks.
Brian Nielsen
