I haven't been able to find another thread here that resolves my problem but apologise if it has been covered and I just didn't find it.
This thread: problems to create clean RAID 1 is the closest I've found to my issue but the solution (use the wipe tool) didn't resolve my issue.
I've just installed OMV (I tried FreeNAS but had issues when the discs started getting full) on my HP Microserver Gen10 and am trying to setup my RAID sets. I have a pair of 500GB discs and I was able to mirror those with no problem. I also have a pair of 2TB discs in there which I also want to mirror and this is where it fails. I have used the "wipe" tool in "Physical Discs" but when I try and create a mirror it creates one of a size 1.82 TB which it then spends a couple of hours resyncing, this is /dev/md1 but it also spawns a mirror 1.23 TB in size called /dev/md1p2 and that has a status of "false". When the 1.82 TB mirror finished resyncing I tried deleting the 1.23 thing but that deleted both of them. I'll see if I can attach a screenshot of this to hopefully explain better.
Any help with this would be greatly appreciated.