Author Topic: Ultra large pools  (Read 532 times)

Offline Norse

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Ultra large pools
« on: September 26, 2017, 01:42:43 pm »
Just wondering what the ideal setup would be for ultra large pools (100TB+) because unless you end up spanning PPU each DRU is limited to 10TB (Most feasible Price per GigaByte of space for a hdd atm).

Without spanning PPU but having two of them you could have quite a few 10TB DRU but of course the more DRU you add as single drives the higher likelyhood you would then be having two of them fail around the same time if you had say 15 DRU and 2 PPU although unlikely two would fail at once does then mean do you just keep adding more and more PPU to have suitable amounts of parity? say 20%?

Would another option be to have hardware/OS Raid 5 on PPU so you can have 6x10TB in two individual Raid 5 appearing to Flexraid as 2 20TB drives meaning you could have 5 DRU of 20TB each instead of 10 individuals, this would mean at "best" case for multiple drive failure you could have 4 drives fail taking out two whole DRU and then  a drive from each Raid 5 fail without losing any data

Am also wondering if anyone here has ultra large pools with drive wise or capacity wise

Offline Brahim

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Re: Ultra large pools
« Reply #1 on: September 26, 2017, 10:30:53 pm »
Is your goal primarily around the pool or the RAID?
If pool, then drive configuration does not matter much.

If RAID, then the tolerance level is what you care for. Spanning PPUs is okay only if you have larger DRUs you are trying to match and vice versa.
However, spanning both DRUs and PPUs just for the sake of reducing UoR (Unit of Risk) count, is not the best option. I personally would go the route of smaller non-spanned RAIDs in Expert mode and then pool all disks from all RAIDS under a single volume.