3par 8400 can't create CPG with drives from both chassis

[ServoPlex]

Hi,

I have a 8440 with 6 FC drives in each chassis in the same slots. It won't let me create a CPG with drives from both chassis. No drives are failled or degraded. I also have SSD drives and experience the same problem.

Just for further info, I can create CPG's with all drives on a single chassis. I am trying MAG level and it doesn't matter which raid level i try.

Any ideas?

[Sheldon Smith]

8440: 2 controllers or 4 controllers?

[ServoPlex]

4 controllers.

[Sheldon Smith]

I guessed as much. It sounds like you have two shelves: One for controller pair 0&1 and the second for pair 2&3.
A CPG defines how the storage (chunklets) is combined into Logical Disks (LD). The Virtual Volumes are created from parts of LDs from all controller pairs.
The LDs are limited to those physical disks (PD) controlled by a specific controller pair.

So, with your current hardware configuration, no CPG using more than one shelf. You would need to add additional pairs of shelves.

As I recall, the 3PAR Concepts guide has more information.

[ServoPlex]

Interesting. I understand the design now. With 4 nodes and 2 shelves, i guess i will put my SSD CPG on one controller pair and shelf and my FC CPG on the other.

Thank you very much for you help and quick responses. I have been struggling with this for days.

[Sheldon Smith]

No. HPE 3PAR Best Practice is to have the drives distributed as evenly as possible between the node pairs.

[ServoPlex]

So i can't have them in the same CPG but i must have the same amount of drives across node pairs? Doesn't this mean that if I have a 4-node system, that i basically always have to have two CPG's for a disk group even though i only need one? Not seeing the benefit of a 4-node system at this point.

Again, thanks for your wisdom and input. It is very helpful.  

[Sheldon Smith]

Ah. A CPG defines how the PD chunklets are assembled into LD RAID sets behind both controller pairs, then all LDs of the CPG are 'sliced and diced' together to make the Virtual Volume (VV) space.

All controller pairs contribute to the VV according to the CPG. Read over the HPE 3PAR StoreServ Storage Concepts Guide available from the Hewlett Packard Enterprise Information Library -- sections on Chunklets, Logical DIsks, Common Provisioning Groups and Virtual Volumes.