I stumbled across this discussion about the
ssd parameter that I'd been using in my installation guide and realized that I was very likely afflicted by what was being disucssed in the mailing list. Firing up IRC and jumping into the
#btrfs discussion on freenode to ask for some clarification about how I'd examine my current state.
Luckily I was able to talk with several knowledgeable people, and even knorrie who was the original author of the mailing list discussion above. I was advised to look at the relative delta between the total and used counts while doing a
btrfs fi df /:
$ btrfs filesystem df / Data, single: total=441.01GiB, used=352.51GiB System, single: total=4.00MiB, used=80.00KiB Metadata, single: total=3.01GiB, used=1.09GiB GlobalReserve, single: total=494.16MiB, used=0.00B
As it was pretty large knorrie suggested that I rebalance, but use his heatmap utility to visualize the progress. So here's how my drive started:
<Knorrie> ok, so bright white is good <Knorrie> and we need to get rid of the dark stuff
Low and behold the results!
$ btrfs filesystem df / Data, single: total=353.01GiB, used=352.52GiB System, single: total=4.00MiB, used=64.00KiB Metadata, single: total=3.01GiB, used=1.09GiB GlobalReserve, single: total=489.78MiB, used=0.00B
If you'd like to do the following, with pictures and videos, check out heatmap. If you'd just like to know how to do the maintenance then I'd suggest the simplest form of balance as:
btrfs balance start -dusage=99 /
btrfs balance start /
you can check on the progress with
btrfs balance status /
This is an entirely ignorant approach and you should consider (like I plan to do in the near future) reading up on how other people are doing maintenance.