I need advice for how to setup RAID for a server that has an array of 16 disks (boot/OS disks are outside this array). In this 16-disks array, all disks are identical (12.8TB SSDs).
The ideal solution for me would be to have at least half the space usable (so, at least 102.4TB out of 204.8TB), and the capacity to resist at least 8 disks failures (any 8 disks should be able to fail without any data loss).
There's no need to see the 102.4TB usable space as a single contiguous volume, so the disks can also be grouped into separate RAID volumes, etc. as long as any 8 disks can break without any data loss.
I was thinking of a couple of solutions, but no solution really satisfies me completely:
The first solution was a single RAID 1+6 volume with 8 spans (76.8TB of capacity, and in the worst case any 5 disks can break without data loss). Scheme:
RAID6( RAID1(D1,D2), RAID1(D3,D4), RAID1(D5,D6), RAID1(D7,D8), RAID1(D9,D10), RAID1(D11,D12), RAID1(D13,D14), RAID1(D15,D16) )
Second solution was a single RAID Z3+1 volume with 2 spans (64TB of capacity, and in the worst case any 7 disks can break without data loss). Scheme:
RAID1( RAID_Z3(D1,D2,D3,D4,D5,D6,D7,D8), RAID_Z3(D9,D10,D11,D12,D13,D14,D15,D16) )
The perfect RAID solution for me would be an octuple parity RAID (like RAID 5 is single parity, RAID 6 is double parity, and RAID Z3 is triple parity), because that would mean 102.4TB of usable space and any 8 disks can break without data loss. But this hypothetical "RAID Z8" doesn't exist, unfortunately.
Thanks in advance for any advice.
P.S.: performance is really not an issue in this case, so it is not a parameter to take into consideration.
P.P.S.: the reason why I seek resistance to any 8-disk failures is because these disks will contain highly mission critical data. Backups are already planned, but still, if the RAID volume stops working, several mission-critical servers and services that depend on it will stop working as well.
P.P.P.S.: high availability of the server itself has already been taken care of.