submitted 7 months ago by [email protected] to c/[email protected]

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Having gradually built up my media collection to near the capacity of my 16TB external HDD, I've reached the point where I'll probably need to build a RAID array to keep the collection in one place. Assuming the RAID array will be at least 32TB, I have a few questions:

From what I've read RAID arrays can help mitigate the risk of individual drives failing if extra space is allotted on the hard drives. Assuming a total capacity of 32TB, how much of that space would be reserved by the RAID array for data loss prevention?
Is there a certain type of hard drive I would have to use? Aside from my 16TB drive, I also have two 2 8TB drives that I'd ideally like to be able to re-use in the RAID array, but have left them in their enclosures for the time being.
If the hard drives in the array have different transfer speeds, does the array as a whole default to the slowest one?
Whether the hard drives I already have are compatible or not, what RAID enclosure and hard drives would you recommend?

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[-] [email protected] 33 points 7 months ago* (last edited 7 months ago)

The general datahoarder hive mind seems to be moving away from shucking and towards manufacturer refurbished drives, see https://serverpartdeals.com/ for example, especially in RAID where you can lose a drive with impunity and warranty is uncomplicated by shucking.

In RAID and similar strategies the redundancy comes from a parity drive, which protects against the loss of one (or more with some schemes) drive, so if you only have two drives of the same size it's just a mirror (50% of total pool) but you can have a drive die without data loss. With four drives you get to use three of the drives (75%), five you can use four (80%) etc. Classical RAID uses identical sized disks but there are other approaches that allow different sizes e.g. mergerfs + SnapRAID or Unraid, here you lose your largest disk to parity.

RAID is generally faster than the individual drives, e.g. mirroring is nearly twice as fast.

Perhaps go with another 2*8Tb which will get you 24Tb usable and use the 16Tb for offline, preferably offsite backup (remember RAID is not a backup, it protects you from disk failure, but not user error for example accidentally deleting things)