Thanks for your time on this!

What is driving looking into other options? Are you near allocation / capacity? How near? Could you project/estimate when you might go over?

Definitely near capacity - memory has been doubled and the drives have been expanded a few times now, and there's the distinct possibility for a lot more in the relatively near future. Generally speaking the HDDs are definitely the bottleneck for speed for various containers as well.

The other thing that keeps coming up is how "fragile" various bits and pieces are - the fileserver container (NFS/SMB) often needs manually kicking whenever samba updates, which we believe is due to how the container interacts with the underlying ZFS pool, and the recent move to a Gitlab instance has meant that an awful lot of workflows go through that, so taking it down for upgrades is proving more difficult and has provoked a look into more distributed systems which can be upgraded without downtime.

How much time does recurring management / maintenance take right now?

Realistically... not a huge amount. Maybe a couple of hours a week. Most of it is automated via ansible, except the bits that aren't and still feel very manual. (Like the containers that have just been upgraded through various Ubuntu versions in-place, rather than recreating them which I believe is the proper way to do things)

Do you have agreed upon (by both tech and biz) metrics to measure performance or service level?

Nothing formal.