If you’re going to add data disks to a linux install, use the UUID rather than the device name (/dev/sda1 etc).

I was adding a volume to my azure VM to use as backup for my local stuff. I added it with the system running and saw it as /dev/sdd. I partitioned it, formatted it etc and saw a nice big 4TB /dev/sdd1. I then added this to my fstab and restarted…

After restarting I took ownership of my /backups mount point without first checking the contents, as it was blank. It turned out that after restarting the device names had jumped around and now sdd1 was my system partition and I had just fsck’ed over my permissions.

I checked into it, and while you *can* try and fix it, there are always going to be some things wrong.
Had to make a new machine, reinstall nextcloud (using nginx this time) and fsck around with moving data from the old data volume to the new one. On the upside, nginx is faster and I now have 4TB for nextcloud.

tl;dr; Always use UUIDs.