For a while, it was either my Jellyfin or my Nextcloud (think NC but not sure) that was running two disks, one for OS and one for data. I forget the details but updating the OS to a new version resulted in a lot of headache.

So I'd be equally interested in the solution to this.

When I talk to teammates at work in engineering, this is usually a use case where they make a network storage. Which, I would think, just moves the problem from the Nextcloud/Owncloud/Jellyfin/etc to whatever is hosting the SMB. But probably that is less of a task to update those systems without borking the whole thing. I've not explored it yet.

Good thinking Landis. Separating your data and the OS in applications such as those you note is a pretty good idea IMO. In fact it's what I have done with my local Media server. It's not perfect because it requires re-initializing the Jellyfin database each time (have to "rescan media") but otherwise it works pretty well.

The way I have it set up is that I have a separate (physical) drive which includes all my media and I mount that to the default storage location (/srv/storage). My media server runs as a VM (with a virtual disk file for the OS). The physical drive is mounted on the host and passed through to the VM. Then I added the disk to the fstab (/etc/fstab) with a new line like this:

/dev/sdb1 /srv/storage ext4 errors=remount-ro 0 1

It's perhaps also worth noting that the Mediaserver appliance is the Fileserver appliance, but with Jellyfin also installed and some other additional tweaks.

ownCloud is a little bit different and I suspect may not be quite as good in that regard. Also, unless you have specific desire for ownCloud, I'd recommend using Nextcloud instead. Nextcloud is a fork of ownCloud that most of the original ownCloud dev team started when the company behind ownCloud made some decisions that they weren't happy with.

I'm not particularly familiar with ownCloud/Nextcloud and I'm not completely sure how well the model we're discussing would work there? The Nextcloud appliance does have a separate "data" directory, but I think that there are still files in there related to the Nextcloud instance itself, rather than just being pure data.

As to OpenVault, that is somewhat like the TurnKey Fileserver, but built from the ground up to essentially be a NAS (Network Attached Storage) device. AFAIK it can run inside a VM, but is more targeted towards hardware install. Under the hood it's Debian (same as TurnKey) but provides it's own web UI and ecosystem of "plugins". So we'll likely never release a TurnKey OpenVault. However, we probably should have a closer look at it for inspiration on additional feature we could consider for our Fileserver.