From Eben King@21:1/5 to All on Mon Apr 21 18:00:01 2025
Hi. I have a 4-disk 5.4 TiB (raw) BTRFS array. It is used pretty much exclusively for backups. Today I backed up the NAS to it. Since there
had been a lot of changes, the total size of the backup was some 300
GiB. During the backup, the "estimated free space" as reported by
"btrfs filesystem usage" dropped as expected, but the "allocated space"
didn't change until I'd written maybe 200 GiB to the array. Is this
expected behavior, or do I need to do something?