Creating a new disk group on EVA8400; resulting capacity

[gurdeep_2]

I have nine 1TB FATA disks in a new disk group; yielding 6415 GB usable capacity (Specifically, Vraid5: 5006 GB).

Question:  it appears it kept 2 for spares; but I only have the "Disk drive failure protection" set to single.

What role was the 2 spares, etc.?
 
 

[Johan Guldmyr]

The single drive protection reserves the equivalent of 2 * the largest of the disk in the disk group.

I don't understand this: "What role was the 2 spares, etc.?"

[Sheldon Smith]

Disk Group protection is always based around vRAID1 usage, regardless of how the disk group is provisioned. vRAID1 is stored as mirrored segments on pairs of physical disks. For each physical disk, the segments are mirrored to a specific alternate.

If the group was fully provisioned with vRAID1 virtual disks, it would take two physical disks worth of space to provide enough storage. Not only are the segments on the failed drive moved elsewhere, but the matching mirrored segments are also moved to the predetermined partners of the receiving disks.

If you set protection to Double, you will see the reserved space increase to the equivalent of four physical disks.