Raid 5 3+1 vs 7+1

[jangoormans]

We have a F400 array, which has 2 CPG of FC. One is raid 5 3 + 1, the other one is 7 + 1. in the properties of the CPG, I see availability is cage, and preferred chunklets is Fast. HP claims that the 3 + 1 should be used to create "fast" disks, with 7 + 1 being the slower tier. is this correct?

[Richard Siemers]

Preferred Chunklets "fast" refers to placement of the data toward the outer tracks of the spinning disk where data moves faster beneath the drive heads, as opposed to the slower inner inner tracks of the disk.

In addition to that, Raid 5 3+1 does perform slightly better than 7+1, but costs more raw capacity for raid overhead.