RE: Guesting (was LPARS/OS)

Sounds quite reasonable. I have a Power 6 M25, comparable to a 520. It
has one hosting lpar guesting two other lpars. I thought of having the
test lpar guest the production lpars (because the test lpar was the first
and only lpar on that box for a spell). But the boss had me do the
unload/reload because he didn't want an IPL of the test affecting
production. And the M25 can be ordered with 2 or 4 lan ports built into
the CEC. And each one of those can support a number of VLANs. Slap on
the HMC (which you already have anyway since you are lparing), dispose of
any insistence on twinax for system consoles, and you can really do this
on the cheap for hardware with minimal slot usage. Our M25's are rack
mounted. On one the two expansion units are just disk. One does have a
fiber card for the tape drive shared by all but that could probably fit
into the CEC - it does have some empty slots.

Drawbacks? You have to consider the length of planned downtime. For
example, on one of our M25's I have one tape drive shared by all lpars.
Two of the three are cluster backups that are only physically backed up
once every other month. So I restrict GUEST1, back up it and bring it
down. Restrict GUEST2, back it up and bring it down. Then I restrict
HOST, back it up, IPL it and then the guests.
And, since I don't omit /QFPNWSSTG from the SAV on HOST I end up backing
up GUEST1 and GUEST2 twice. Once with the granular GO SAVE 21 on each,
and the second time with the data in /QFPNWSSTG as one big lump.

I could reduce this a little by

- Getting a tape drive for GUEST1 and a different tape drive for GUEST2 to
do the saves of them simultaneously.

= Omit the /QFPNWSSTG from HOST
or
= Not doing the full save on either GUEST1 or GUEST2 and rely completely
on /QFPNWSSTG from HOST. I am a bit loath to lose all granularity (even
if it is only done every other month).

I haven't played with omitting /QFPNWSSTG from HOST and leaving GUEST1 and
GUEST2 powered up and trying to save all lpars at once.

Other drawback: Must be Power 6 hardware running 6.1. Look at that as a
benefit though. :-)

We also used to guest all Linux partitions. But that confused IBM support
running IBM's TSM on Linux on IBM i on IBM Power equipment. And, at the
time, I did not have a strong enough advocate to knock their heads
together and tell them to get over it. So we dedicate these Linux
partitions. Probably would not do that again (I've made some additional
contacts).

Rob Berendt