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What if NAS is down?

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I understand that using NAS's RAID 5 feature with minimum 3 drives, if one of the drive is down, the NAS will still function. I can get a replacement drive for the NAS back to normal.


What if the whole NAS hardware is down and is not serviceable? If I plug the hard drives into another NAS box will the data be intact? My guess is it will still work if I put the drives into the same model NAS. What if my NAS is three years old and I can not buy back the same brand and model?


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Sorry to repeat the well worn phrase, but RAID is not backup. The idea is 'availability', guarding against the most likely source of failure, the hard drive. Note that in commercial implementations, cabinets of RAID disks may well also have redundant, hot-swappable power supplies, so if a single power supply fails, power will be uninterrupted. This guards against the next most likely point of failure. You don't get redundant power in domestic RAID boxes...


Would transplanting all of the disks out of a cleanly shut down, functioning RAID array, into a brand new identical RAID array, work? I have no idea, but I wouldn't want to try it, let alone have to rely on it. There could be hardware/firmware version differences even between RAID NASs of the same model. Individual drives may expect to be in a particular slot, and expect other slots to contain particular drives (guessing a bit here, but you cannot assume it will work). RAID's purpose is to maintain availability of the array more than anything else, such as making the array's data rise from the ashes in a new array.


RAID is very convenient backup of sorts, in the sense that if a drive fails and can be rebuilt, then by yanking the broken drive and putting in a spare, there is no easier way to do a restore. But you still need (at least one) separate backup, stored safely elsewhere from the NAS, to have a good level of protection, you need to keep it current, and you need to know how you would restore it. If the NAS fails completely, that's what you'd use.




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