We have a HUS 130 on microcode version 0980/D-S. I have a full tray of 24 disks with the same type of drives 600GB 10K SAS.
I wanted to create a DP Pool of RAID 5, with (4) 5D+1P disk combinations as this will utilize the full tray capacity and should provide performance.
In the past (2+ years ago), I thought Hitachi had a best practice for optimal performance for Pools by adding disks in even number combinations (2D, 4D, 6D, etc) or keeping disks to combinations of 4 or 8, meaning 2x2, 4x4, 4x1, 8x1, 8x2.
Is this now no longer the case with my updated firmware version and (4) 5D+1P disk combos would work well?
Also, what is the difference between Shrinking a DP Pool capacity vs Deleting the DP Pool? I have no data/volumes on this pool yet but I need to recreate my disk combinations - not sure if I should select all my RAID groups and "Shrink Pool Capacity" or just delete my entire pool and start fresh.
Thank you!
The idea of creating traditional raid groups with even numbers of data disks is an old one to do with cache segment and disk strip size optimization. Cache is plentiful enough these days that this is not generally considered to be that important in such small configurations, however it is recommend that when creating an HDP configuration that the number of rg's in a pool are in multiples of 2 or better still, 4 where possible.
As for shrink and delete, delete will destroy your data and return all disks in the HDP to unallocated status, skrink will remove the last RG from the HDP but will first have to re-stripe your luns data across the remaining rg's. HDP shrink is quiet time consuming and obviously requires that you have surplus capacity in the pool to accomplish this.