ME4 ADAPT Usable Space Formula

Question

Hello all, I'm trying to find some more information about the ADAPT RAID level with the ME4 Series. From what I can find ADAPT will set aside the capacity of your  2 largest drive for spare, however, what I'm having difficulty finding is the overall usable capacity of an ADAPT disk group. For instance, if I have a Disk Group of 50 - 1TB Drive, I know 2TB will be set aside for sparing but I can't find information on how much of that left over 48 is usable. If it was something like RAID 1 or 5 or whatever, I could easily calculate it out knowing how those store the data. I just can't seem to find anything like that for ADAPT.   Does anyone know? or could someone point me in the right direction?

DELL-Sam L · Accepted Answer

Hello DaveyG75,

With Adapt raid uses raid 6 configuration 8+2. If you were to calculate your space using raid 6, you can find out how much space you will have.

Please let us know if you have any other questions.

DaveyG75 · Answer

Sorry if this sounds dumb, but just to verify.

With my 50 - 1TB disks...

50TB - 2TB = 48TB

Then I need 20% of that 48 for the Parity, so 9.6TB

Final Usable - 50 TB - 2 TB = 48TB - 9.6TB = 38.4TB when I account for spare+parity

DELL-Sam L · Answer

Hello DaveyG75, 38.4TB is correct on the space. Please let us know if you have any other questions.

Olainen · Answer

That makes sense now. I was just removing 4 disks from the pool and calculated the size which never was right.. (N-4 X TB).
So I've got my formula now: ((Ndisks - 2)*DiskSize)-20% = Usable disk space with ADAPT

PowerVault

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