Superdome - Allocation of CPU's in a partition

[Manjunath_3]

Hi

I currently working on a superdome which has 2 partitions. On one partition we want to increase the CPU(from 6 to 10) and Memory(from 10Gb to 16Gb). We have 2 cell boards currently and will install the 3rd. After the upgrade w.r.t cell boards it will be

4CPU+8GB Ram X 4CPU+4GB Ram X 2CPU+4GB Ram

Question is,
1. Will we(HP engr) be able to activate the CPU's on a cell as requested above(4*4*2) or does the CPU gets evenly ditributed across the cell boards.

2. w.r.t memory, HP recommends that it needs to be same across the cell boards, otherwise it will affect the performance. Does that apply to CPU as well? Any doco related which explains the performance impact?

Will summarise,

Regards,
Math

[Stefan Stechemesser · Accepted solution]

Hi Math,

the rules only point you to the OPTIMAL configuration regarding performance. That does not mean that other configurations are extremely slow. It depends on your memory usage if you could measure a performance impact from an suboptimal configuration.
The Cells in a Superdome Partition are configured for Memory Interleaving and the Interleaving is optimal if the memory is spread equally across the Cells. In newer Systems (Integrity Superdome / Superdome PA8800) you can configure either interleaved memory or cell local memory, depending on you kind of application (number of CPU used, memory blocks used) and it is not easy to tune the system for optimal performance.

The CPUs do not do any interleaving like things. The only performance rule is that the CPUs on one Cell are faster connected (Cache to Cache transfers etc.) than the CPUs on different Cells (the data packets have to run through the backplane), so I think you will have the best performance with your configuration (as many fully populated Cells as possible), but as I already said, it depends on your application if you will measure a performance difference.

Do not forget that there are also performance rules regarding what Cells should be choosen for a partition ...

Best regards

Stefan

[Manjunath_3]

Hi Stefan,

Thank you so much for the info. It was very helpful. Also thank you for pointing out on the performance rules reg the cells for partition. It made me refer to the doco "Managing superdome complexes" which was quite useful.

Best Regards,
Math