lpar min/desired/max values

[mrn]

Hello,

I'm working on a site where we build lpars with figures given by a system designer. E.g.

mem = 32
cpu = 4

just wondering what the rest of you guys do about min / max figures, I've read through various redbooks and don't see any formula for what they should be set to. Normally I would half and double for min & max and double for virtual procs; which is fine until you start using small numbers (as in 0.1 of a cpu).

Anyone got any clear guidance?



Mike

"Whenever I dwell for any length of time on my own shortcomings, they gradually begin to seem mild, harmless, rather engaging little things, not at all like the staring defects in other people's characters."

 

[p5wizard]

For memory, it is best not to oversize max value, because then the overhead may grow out of proportion: the partition memory page table needs to be big enough to account for to max memory size

So estimate how big the LPAR needs to be for memory, subtract X for min size, add X for max size, X being dependent of your initial estimate and how good that estimate is.

8GB or less: X=2 -> 6-8-10
16GB or less: X=4 -> 12-16-20
32GB or less: X=8 -> 24-32-40

You can always change the values later on and on next activation of the profile, they come into play.

For shared processor LPARs CPU entitlement, I always set 0.1-x-N with N being the max number of CPUs configurable (e.g. 16 for a 570)
virtual CPUs: 1-n-Nx2

n using about .2 to .3 of a CPU
N as above

E.g. for a small uncapped 0.5CPU LPAR on a 570:

entitlement: 0.1-0.5-16
virt CPUS: 1-2-32 OR 1-3-32

Unnecessary virtual CPUs are folded down in AIX53 (as of TL3 I believe) anyway to reduce the number of context switches. The number of virtual CPUs available limits the uncapped-ness of an shared processor LPAR

For a capped LPAR, it doesn't matter: You can have just enough virtual CPUs to be able to burn the CPU entitlement...


HTH,

p5wizard