@dvdhngs
Run lvscan to see if there are any active logical volumes. If there are run vgchange <group name> -an to deactivate all logical volumes. Now try to stop the array.

@olivierlambert
I wasn't suggesting that the installer should do raid 10 necessarily. For XCP-NG itself raid 1 is sufficient. Just suggesting that the partitions of the installation could each be a different raid 1 set rather that simply doing raid 1 on a whole disk basis. If the end user chose to have the installer create local storage it could be just raid1 on another (big) partition. For those who want improved performance however there is the possibility to manually create raid 10 local storage post install.
What is wireframe? (I am not a developer).

@olivierlambert
Glad to be of help. The new raid installer is a really good thing and I am using it now on two servers. The downside, however, is that it uses whole disk raid. If it used partition based raid1 then if XCP-NG were installed without local storage repo, it would be possible (after installation) to manually create raid 10 for the storage. With mdadm this could be done with three or more disks. So at that point all the installation partitions would be raid1 with all disk partitions as members but the bulk of each disk (assuming large disks) would be left unused for raid 10 - faster local storage. Would that be an over complicated change to the installer or is this a possibility?

@olivierlambert
Probably that would work or as an alternative use dd to zero the first 45GiB of each disk shouldn't take too long. I was not pressed for time and had other things to do so I just zeroed the disks entirely after which setup was flawless.

@olivierlambert
Hmmm. It might have been 0.9 as it was for boot partition. It wasn't whole disk raid though. Each partition was a different raid set.

@olivierlambert
I did that Olivier but for me it didn't work. That's why I zeroed both disks entirely. Worth a try though as it doesn't take long.

For me it was old mdadm superblocks. Once the partition tables have been deleted they could be anywhere depending on the original raid setup. Best thing is zero the entire disk.

dd if=/dev/zero of=/dev/sdx bs=1M status=progress
where x is your drive letter.

Do this for each raid disk
Then go and drink some beers. It will take some time...