AIUI this model (2014 vintage) uses a 32-bit ARM CPU and thus has a hard limit on volume size of 16TB. I currently have 4x5TB for a usable volume of 15TB. 5TB drives are becoming difficult to obtain so when disks fail I need to replace them with larger units. I have had one failure, and replaced it with a 6TB unit, albeit using only 5TB of that disk. I know that if I replace all four with 6TB units, I can't expand the volume to 18TB, but if I were to replace them with 8TB disks, could I create an additional volume in the remaining space? That is to say, is the documented 16TB limit on these units total usable capacity or just individual volumes?
is the documented 16TB limit on these units total usable capacity or just individual volumes?
There was a 16 TB limit early on, but that was removed a long time ago (in the 6.4.0 firmware released Oct 2015).
So you can go with larger disks.
Avoid desktop class though - many models (including some Seagate Barracudas) are SMR. You also want to be careful with WD Reds in the 2-6TB range. The newer EFAX series uses SMR technology. The older EFRX are fine (as are EFAX drive 8 TB or larger). Ironwolf drives are good choices.
