On 1/21/09 2:20 PM, "Tom Duerbusch" <[email protected]> wrote:

> You said that if you used dedicated disks, you will now pay for it.
> I'm interested in "why you would pay for it"?

Mostly because it's usually a sign of a we-like-LPAR-LPAR-good mindset, and
you then fall into the problem of "it's a new disk, so it's a new address in
the guest because then the CP directory matches the actual physical disk"
and you have to muck around with the parm files in Linux and it's generally
a good sign that the whole project is going to be a enormous PITA.

I also really prefer to let VM manage the actual cyl 0. That may be just
that I'm ancient and weird, but that way, there's absolutely zero chance
that something weird in Linux will cause something unpleasant to happen to a
disk that some other OS cares about, and there's zero chance of some yoyo
creating duplicate volids on the physical system, which could impact the
operation of the entire environment (cf the discussion about what order
multiple DRCT areas get interpreted if you want to see how random that can
get)

> Now, if you were thinking LPAR, when then, yes, I agree it is much more
> complicated.

If I haven't said it before, I don't think there's much reason to ever
consider LPAR deployment of Linux, but others do disagree with that view.
I'm sure there are workloads where it would matter, but I still think the
manageability loss dramatically overwhelms any cost advantage from omitting
VM.

But, you're right -- standalone DDR in LPAR is an even larger PITA.

-- db

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