Years ago I bought 2 x Seagate 2TB SSHD (ST2000DX001) to use in my PC. I've since moved over to SSDs and decided to create a NAS with them for network storage in a RAID 1 config. The drives will inevitably fail at some point so I want to get a spare for when that happens. This particular model is obsolete now and can no longer be bought easily (not for an inflated price anyway). I'm assuming most 2TB drives aren't exact and if I get one that has a capacity slightly less then I won't be able to use it to rebuild the array during a drive failure? Is there any easy way to find a suitable replacement model than simply resorting to much bigger drives? I'm not bothered about any performance loss from a slower or mismatched drive.