On 4/21/25 18:36, Anders Andersson wrote:
On Mon, Apr 21, 2025 at 9:32 PM Eben King <e...@gmx.us> wrote:
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?
Just a quick preliminary guess: The filesystem have previously been
large enough to use those 200 GB, and even though you then removed
some data it doesn't release allocated blocks immediately when they
become unused, but keep it for future use.
I periodically run "duperemove" on that array. Could that account for
this? Also, is there a way to resize the filesystem so writes are
reflected immediately?
