Sparing question with multiple drive sizes

[mangoman]

Hello,

Consider the following please:

I have an EVA6000 with 64 drive bays populated and double drive failure protection on a single disk group.

In the 64 drive bays are:

16 x 600GB FC

16 x 450GB FC

32 x 300GB FC

I have recently retired another EVA that was populated with 146GB FC drives and would like to use those and bring my 6000 to the full 112 disk capacity.

48 x 146GB FC

I know that in reality that the 146GB drives are in fact 136.73GB.  48 x 136-73 = giving a raw capacity of 6.563TB.  However some space on each drive will be required for sparing capacity.

Is my calculation below correct:

600GB (The largest drive in the group) which is actaully like 550GB (estimating) * 2 = 1100GB * 2 = 2200GB.  So 2.2TB are required to be reserved for double failure protection.  Spread that across all 112 drives = about 20GB per drive lost as reserved for protection leaving me 116GB to use on these 146GB drives.

Or is the protection space reserved on each drive relational to the size of the drive so the 600GB drives might set aside 80GB for spare protection and the 146GB drives set aside 5GB each?

[Sheldon Smith]

EVA disk usage is proportional to size. After any leveling is complete, all disks should show the same percentage occupied. And as far as I've ever been able to tell, the reserved protection space is just a number subtracted from the total capacity of the disk group.

Click the Kudos star if this helps.