I currently have bays 1 and 2 using identical sized 500GB HDDs, they are setup in mirror configuration.
I am looking to replace each of these disks with 2TB capacity, and retire the old ones.
Having thought about it, would it work if I took bay 2 drive out and inserted the 2TB disk, then I imagine it would sync the bay 1 volume to new bay 2 disk? Assuming this happens, I can substitute bay 1 HDD with a fresh 2TB disk, and bay 2 should sync to bay 1?
What I ended up doing is inserting a new 2TB disk in bay 3, and what has happened is that it how has 950GBs of storage
Should I remove bay 3 disk, format it, then do above drive substitution?
Having thought about it, would it work if I took bay 2 drive out and inserted the 2TB disk, then I imagine it would sync the bay 1 volume to new bay 2 disk? Assuming this happens, I can substitute bay 1 HDD with a fresh 2TB disk, and bay 2 should sync to bay 1?
Should I remove bay 3 disk, format it, then do above drive substitution?
Unfortunately that won't work now, because you've already added it to the array. If you try it, you'll lose all the data.
If you have an NV+ v1 (running 4.1.x firmware):
What you need to do now is copy all the data off the NAS (perhaps onto the second 2 TB drive). Then do a factory reset with just the first 2 TB drive installed. Rebuild the NAS, reload the data from the backup. Then hot-insert the second 2 TB drive into slot 2.
If you aren't running current firmware, you should upgrade to 4.1.15 first.
If you have an NV+ v2 (running 5.3.x firmware):
The simplest thing is to hot-insert the second drive into slot 4. That will expand to a 3 TB total volume size. Though if you are worried about the health of the 500 GB drives, then use the v1 procedure above.
