Re: Virtual disks for an i partition

Pete, a bladecenter-s (BCS) is a little bit of a different critter than the servers Pete, Larry, and Rob work on. That said, here are some answers to your questions.


On 2/11/2013 3:54 PM, Pete Helgren wrote:

I seem to recall that the recommendation for VIOS installation use two
mirrored physical disks but now I am not so sure that is necessary if
the 6 320 GB drives in the SAS cage were one volume and then two
smaller virtual disk were carved out for VIOS. Is my assumption about
physical disks for VIOS incorrect?

Yes, VIOS should protect the disk used for rootvg. However, if my memory serves me, you will use the disk on the blade for rootvg, not the disks in the BCS, so protecting it becomes problematic because there's only 1. (My memory may be failing me on that point! There may be 2 disks on the blade, in which case, you would run mirrorios to get disk level mirroring.)

If I understand Rob and the good Doctor correctly, I should carve out at
least 6 virtual disks for IBM i? Then in IBM i I also create a RAID
array from those 6 disks (or is that redundant?)

IBM i cannot "turn on RAID" protection for the drives in a BCS. You will either create parity sets from VIOS or you'll give the drives straight to IBM i and use mirroring to protect them.

Regardless, if you need good save/restore performance, you certainly want to have at least 6 "disks". If save/restore isn't critical, you can get by with 2-5 "disks". My testing showed that getting to 6 drives cut average save/restore times in half when compared to any configuration of fewer disks.

I guess I never fully virtualized my thinking: The configuration of IBM
i on VIOS should mimic a physical configuration. Yes?

With the BCS hardware, you can have it mimic a physical configuration, but it doesn't have to.