On 12-02-26 02:19 AM, Jérôme Poulin wrote:

What would be interesting is getting an eye on btrfs fi df of your
filesystem to see what part is getting full, or maybe just do a
balance.

I did try a balance.  As I had mentioned subsequently, I ended up having
to grow the filesystem to 10x (somewhere between 20 and 50GB) it's data
requirement in order to get that kernel headers .deb to unpack, and
after it unpacked I was successful in shrinking back down to 5G, so it
seems the problem was something worse than just "not ideal" metadata
allocation.

I have been running 3.0.0 for quite a while without any problem,
metadata grew a bit too much (1.5 TB for 2 TB of data) and balance
fixed it back to 50 GB of metadata then 20 GB after deleting some
snapshots.

Interesting data point, thanks.

b.