Should I buy matching hard drives for a NAS RAID 1 array?

"A general rule-of-thumb is to have matching disks in the array. The characteristics of each manufacture will differ, so the more similar the disks, the less like the RAID controller will have to deal with data corruption. That said, you don't have to use matched disks. For instance, make sure you replace a failed disk with another the same size or larger.

I wouldn't be concerned with 2 drives from the same manufacturer dying at the same time. The odds of that happening are tremendous -- probably equal to that of 2 drives from different manufacturers dying at the same time.

Now, if you're worried about protecting your data, please make sure that you don't solely rely on your RAID1 array. It is not a backup solution! Make sure you backup your important data, take it offline, and take it offsite."

"I've actually experienced two drives from the same manufacturer crashing at the same time.
It's extremely rare though, but I'd still consider getting different drives on my next storage solution, or go for some higher reliability drives (if such a thing really exists)."