Thats what I was also running, then had a drive start dying on my, pulled it, replaced and as the rebuild start it failed, zero’d the drive, tried again, it did the same thing, but now it caused a problem on a 2nd HDD’s leading to the volume crashing.
Rebooted the server, and it came back, and it’s been on ICU status since.
The way xPenology handled all of this, and the restriction of where a drive sits, and have to sit, (cast in stone) → Problem.
Well rebuild server as a TrueNAS and it seems the problem was not the HDD’s but rather 2 SATA ports. I had to replace the PSU 2 weeks ago, this is where everything started, server at random shut down, started it up and it was good for a couple of days, and then dead again, figured PSU is bad, so replaced that, but looks like the PSU damaged the MB/SATA ports along the line.
I did like xPenology… DSM interface was slicker, and SHR def saved my @ss, but getting to grips with TrueNAS Core quickly, rebuild my Unify Controller in a Jail quickly and same for my Plex Media Server.
I picked up (figured out that this was the problem causing xPenology crashing the volume) the bad Sata ports while copying the data (from backups back onto the TrueNas) and got to say all I had to do was shut down the NAS, move the HDD to another port and bring it back, I for safety sake also swopped out to another spare HDD, TrueNAS did not skip a beat, it came back said degraded pool, click on wheel, go repair and it did the resolver all I continued to copy data (come xPenology) can learn a thing or 2 here.