Hello James,

I'd take a look at the VNX2 best practices for performance white paper here:

https://support.emc.com/docu42660_VNX2-Unified-Best-Practices-for-Performance---Applied-Best-Practices-Guide.pdf?language=en_US

Quoting from page 17:

Recommendations for creating and expanding storage pools:

• When creating a pool, it is best to specify a multiple of the preferred drive count for each tier you configure

          o For example, when using RAID 5 4+1, specify a drive count of 5, 10, 15, etc.

• It is best to maintain the same capacity and rotational speed of all drives within a single tier of a given pool

          o For example, AVOID mixing 600GB 10K SAS drives in the same pool with 300GB 15K SAS drives; instead, split them into 2 different pools

• Within a given pool, use all of the same flash technology for the extreme performance tier
• When expanding pools, use a multiple of the preferred drive count already in use for the tier being expanded

Hope it helps,

Adham

Many thanks

J