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I'm looking into building a NAS for file storage, and I'm trying to determine the right scenario for my use case. I'm looking for about 32TB of raw storage, and no less than 16 useable given a redundant RAID array. I'll mostly be accessing files that are at least 500MB, up to 75-80GB. Right now I'm seeing a 4TB*8 drive array or an 8TB*4 drive array as my best options: it's about the same cost (larger array is $20 more), storage space isn't an issue, and the drives are NAS optimised, so I'm not concerned about heat or vibrations.

My NAS will be in one place, and I'll be remotely accessing files from another location (5 users at a time, or thereabouts), with network speeds of about 100Mbits/second consistently. I'm seeing RAID 10 or RAID 6 as my safest and most viable options, alongside a 16TB offsite backup once a month in cases of corrupted data within the array. Processing power shouldn't be an issue, so I can't see calculating parity as being a major roadblock. RAID 10 would drop me to my minimum of 16TB storage, with excellent reads and writes, but I don't know if those would matter at all if my network is the theoretical bottleneck anyway. RAID 6 on the 8*4 would also bring me to 16TB. RAID 10 on the 4*8 array grants me 16TB of storage, with more theoretical throughput, as there's striping between more drives. RAID 6 on the 4*8, however, gives me 24TB of storage, 2 drive parity, ease of replacement (1 drive failure is half the cost of the other array), and an easier time rebuilding the array should a drive failure occur (less storage per drive). Am I missing something? Are there advantages to a smaller array with higher capacity drives, besides the aspect of portability and size (which shouldn't be a problem here, as the array isn't moving)? Thanks!

Fluoroantimonic Acid
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  • You're right about R10 and R6/60 being the only choices, if you need better random-read performance go for the 8 x 4TB, if you don't care about performance then I'd go for the 4 x 8TB option to give you more slots for future expansion. – Chopper3 May 02 '18 at 16:24

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I’d personally go for the 4 x 8TB option. That way you can have it in RAID10. Granted your rebuild times will be longer but 16TB of redundant storage and not losing anything to parity isn’t bad

Timothy Frew
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  • RAID 10 has no drive limitations, so wouldn't I be able to run either configuration in RAID 10? – Fluoroantimonic Acid May 02 '18 at 22:33
  • Well it doesn’t, you’re right but you’d be giving up a bunch of disks and not getting more space. As you can’t combine 4 disks in a raid 10 either side to get double storage effectively. It would just be three drive tolerance on each side of the array which is beneficial but not all that worth it. As long as you proactively monitor the disks and have proper monitoring on the host for IO issues that might indicate drive failure the. You should only require one fault in each pair of the raid10. – Timothy Frew May 02 '18 at 22:46
  • If you suffer catastrophic drive failure resulting in half the arrray going away and unrecoverable that’s when your backups come in. I know this isn’t your specific intention but massive raid arrays with little benefit other than multiple drive fault tolerance is not a replacement for backups banking on you’ll never lose the data. If that makes sense. – Timothy Frew May 02 '18 at 22:50