Mixing different P4000 capacities in one cluster

[Paul Miano]

I have 4 2120 NSMs (G1 and G2) each with 3.6TB capacity. I am planning for future expansion and hardware refresh once the nodes become unsupported.

Supposition: If I were to add a additional 2 5.4TB models I believe they will only format to the 3.6TB (or 2.6TB usable) as the other nodes in the cluster. This would strand the remaining capacity.

Question: Over time as I'd replace the other 3.6TB nodes with 5.4TB, would I be able to reclaim the stranded storage?

[teledata]

Once you remove the last of the 3.6TB modules from the cluster, It would no longer have stranded storage.

You can move new nodes into your cluster, and old nodes out in 1 step, so you only incur the re-stripe process once. (you remove the 2120, and add the new modules, once it is done re-striping, the legacy 2120 would be "available" for you to create a new cluster with them

Another option would be to use the Starter SAS modules. You would be buying less stranded capacity.

2120 12x300GB SAS in RAID 50 = 2.67 per module

STARTER SAS SAN (8x450) usable in RAID 5 = 5.62 or 2.81TB per module (only about 140GB stranded)

Be aware mixing the 8 disk Starter SAN would lower the effective IOPs of the 2120 units, because they would be in the same cluster they can't crank out more IOPs than the 8 disk STARTER SAN modules.

Obviously the 4500 models are better for IOPs, rack and power density, but the SAS Starter bundles are pretty attractively priced. The other consideration is the "Virtualization SAN" bundle comes with 10 VSA licenses if that is of benefit for you.

Here's a quick calculator I created:
Current models:
http://www.tdonline.com/hp-lefthand/storage-calculator/

Legacy (NSM and LeftHand modules):
http://www.tdonline.com/hp-lefthand/legacy-calculator/

[Paul Miano]

That confirms what I thought. Interesting calculators on your website, as well as the other information. I think I'll have to keep that in my back pocket as I get quite a bit of questions about the what, where and whys of my setup. Thanks.

Paul