# LPAR CPU Utilization - Aix

This is a discussion on LPAR CPU Utilization - Aix ; Situation: System Name Min Desired Max LPAR1 1 1.5 2.0 LPAR2 0.5 1.0 2.0 LPAR3 0.5 1.0 2.0 1) If the frame has 2 overall CPU , would itbe able to start all three lpars on boot ? starting with ...

# Thread: LPAR CPU Utilization

1. ## LPAR CPU Utilization

Situation:

System Name Min Desired Max
LPAR1 1 1.5 2.0
LPAR2 0.5 1.0 2.0
LPAR3 0.5 1.0 2.0

1) If the frame has 2 overall CPU , would itbe able to start all three
lpars on boot ? starting with the minimum CPU.

2) If the frame has 3 CPU can it start the first two with Desired and
thrid with minimum conf ?

When the LPAR boots , does the checking process start with first
chcking desired and if there is no desired available then it would

Ciao

2. ## Re: LPAR CPU Utilization

"invincible" wrote in message
> Situation:
>
> System Name Min Desired Max
> LPAR1 1 1.5 2.0
> LPAR2 0.5 1.0 2.0
> LPAR3 0.5 1.0 2.0
>
> 1) If the frame has 2 overall CPU , would itbe able to start all three
> lpars on boot ? starting with the minimum CPU.
>
> 2) If the frame has 3 CPU can it start the first two with Desired and
> thrid with minimum conf ?
>
> When the LPAR boots , does the checking process start with first
> chcking desired and if there is no desired available then it would
>
> Ciao

Since nobody else has responded yet here is my guess based on my
understanding of how it works:

Case 1:
On boot CPU will be allocated to LPARs based on the Desired amount, and then
based on the Min amount, so LPAR1 would get 1.5, LPAR2 would get 0.5, and
LPAR3 would not start. I'm not certain on the order that LPARs start but I
think there is some weighting involved.

Case 2:
Yes. Same algorithm,. LPAR1 gets 1.5, LPAR2 gets 1. LPAR3 gets 0.5.

This is my understanding from reading the documentation, we have the
allocation set so all LPARs have desired set such that the sum is equal to
the box capacity. Now I have no idea what happens if PLM kicks in soon
after boot, but before all LPARs are started.

3. ## Re: LPAR CPU Utilization

On May 21, 9:27 pm, "Bruce" wrote:
> "invincible" wrote in message
>
>
>
>
> > Situation:

>
> > System Name Min Desired Max
> > LPAR1 1 1.5 2.0
> > LPAR2 0.5 1.0 2.0
> > LPAR3 0.5 1.0 2.0

>
> > 1) If the frame has 2 overall CPU , would itbe able to start all three
> > lpars on boot ? starting with the minimum CPU.

>
> > 2) If the frame has 3 CPU can it start the first two with Desired and
> > thrid with minimum conf ?

>
> > When the LPAR boots , does the checking process start with first
> > chcking desired and if there is no desired available then it would
> > start with the minimum ?

>
> > Ciao

>
> Since nobody else has responded yet here is my guess based on my
> understanding of how it works:
>
> Case 1:
> On boot CPU will be allocated to LPARs based on the Desired amount, and then
> based on the Min amount, so LPAR1 would get 1.5, LPAR2 would get 0.5, and
> LPAR3 would not start. I'm not certain on the order that LPARs start but I
> think there is some weighting involved.
>
> Case 2:
> Yes. Same algorithm,. LPAR1 gets 1.5, LPAR2 gets 1. LPAR3 gets 0.5.
>
> This is my understanding from reading the documentation, we have the
> allocation set so all LPARs have desired set such that the sum is equal to
> the box capacity. Now I have no idea what happens if PLM kicks in soon
> after boot, but before all LPARs are started.

thankyou Bruce for the clarification

4. ## Re: LPAR CPU Utilization

On 21 mei, 13:51, invincible wrote:
> Situation:
>
> System Name * * *Min * Desired * Max
> LPAR1 * * * * * * * * 1 * * * * 1.5 * * * 2.0
> LPAR2 * * * * * * * * 0.5 * * *1.0 * * * 2.0
> LPAR3 * * * * * * * * 0.5 * * *1.0 * * * 2.0
>
> 1) If the frame has 2 overall CPU , would itbe able to start all three
> lpars on boot ? starting with the minimum CPU.
>
> 2) If the frame has 3 CPU can it start the first two with Desired and
> thrid with minimum conf ?
>
> When the LPAR boots , does the checking process start with first
> chcking desired and if there is no desired available then it would
>
> Ciao

Th IBM redbook SG247039 "Partitioning Implementations
for IBMEserver p5 Servers", chapter 3.4 Partition Load Manager is
quite clear on this

5. ## Re: LPAR CPU Utilization

On May 21, 5:51*am, invincible wrote:
> Situation:
>
> System Name * * *Min * Desired * Max
> LPAR1 * * * * * * * * 1 * * * * 1.5 * * * 2.0
> LPAR2 * * * * * * * * 0.5 * * *1.0 * * * 2.0
> LPAR3 * * * * * * * * 0.5 * * *1.0 * * * 2.0
>
> 1) If the frame has 2 overall CPU , would itbe able to start all three
> lpars on boot ? starting with the minimum CPU.
>
> 2) If the frame has 3 CPU can it start the first two with Desired and
> thrid with minimum conf ?
>
> When the LPAR boots , does the checking process start with first
> chcking desired and if there is no desired available then it would
>
> Ciao

My understanding (from class) is as follows:

The minimum is the minimum amount of hardware you can take the LPAR
down to, i.e. the minimum it needs to run. The desired amount is what
it will attempt to allocate, the max is the maximum amount of
resources it can be given. The LPARS start based on the Desired
value. The only time the minimum becomes important is if you are
dynamically deallocating hardware, the minimum sets a limit on what
you can take. The maximum value does the same for what you can give
the LPAR.

Based on your example, (assuming you bring up your frames in numerical
order) if your frame has 2 CPU's, LPAR1 would start, but the other two
would not. If your frame had 3 CPU's LPAR1 would start, LPAR2 would
start, LPAR3 would not. The weight value of your LPARs determines
which LPAR has priority in grabbing available resources. How you
weight your LPARs also changes how they will come up. If LPAR3 had
the highest weight (the default is 128) then it would come up first
regardless of the state of the other two, and it would also grab any
free resources first to meet the Desired requirements to come up, if
it was able.

I strongly recommend reading the Redbook on it...and getting your
hands on the HMC guide, which has a good overview of weighting and
Desired vs Min vs Max.

I hope this helps answer your question.