I have quite a few spare old 500GB WD Black disks that I'm going to be using for the root file system of a FreeBSD NAS at home. These disks have been in continuous use for 5 years within a rack server at work, so I don't consider them very reliable. Since I have lots of spare 3.5" bays while starting out with the NAS, I was thinking of having a 3 way ZFS mirror as my root file system using these old disks.
My goal is to buy a pair 2.5" disks for the file system once I'm not that strapped on cash. My question is then that if I buy different disks, is there an easy way to set up the ZFS file system, so that I can just add the new 2.5" disks to the pool, let it resilver, and just remove the old 3.5" WD Black disks? This would save me from having to reinstall the OS.
The point here is that the new 2.5" disks might have any size, but be large enough to contain all the data on the OS partition.