Hi,
Read on another post that you can use sudo btrfs fi du -s
<pathtosnapshot>' to get a report on how much exclusive space is
being used by the snapshots, I wasn't aware of this command and
believed that there wasn't an easy way to get this, but after using it
on some of my btrfs file systems used for backups it seems unreliable.
This file system is used to backup one of my desktop disks where I
temporally save mostly large multimedia files to later archive to
another server, everyday before making the backup I do a snapshot, so
there are practically no modified files, only new or deleted files,
these are just a few days of snapshots:
btrfs fi du -s /mnt/disks/BackupSS/snaps/sspaces_daily_2018-07-2*
Total Exclusive Set shared Filename
199.98GiB 648.22MiB 199.35GiB
/mnt/disks/BackupSS/snaps/sspaces_daily_2018-07-20-070001
198.74GiB 2.45GiB 196.29GiB
/mnt/disks/BackupSS/snaps/sspaces_daily_2018-07-21-070001
277.13GiB 0.00B 277.13GiB
/mnt/disks/BackupSS/snaps/sspaces_daily_2018-07-22-070001
277.13GiB 0.00B 277.13GiB
/mnt/disks/BackupSS/snaps/sspaces_daily_2018-07-23-070001
80.04GiB 2.44GiB 77.60GiB
/mnt/disks/BackupSS/snaps/sspaces_daily_2018-07-24-070001
93.71GiB 1.17GiB 92.55GiB
/mnt/disks/BackupSS/snaps/sspaces_daily_2018-07-25-070001
94.85GiB 0.00B 94.85GiB
/mnt/disks/BackupSS/snaps/sspaces_daily_2018-07-26-070001
339.82GiB 127.77GiB 212.05GiB
/mnt/disks/BackupSS/snaps/sspaces_daily_2018-07-27-070001
279.94GiB 79.69GiB 200.25GiB
/mnt/disks/BackupSS/snaps/sspaces_daily_2018-07-28-070002
118.00GiB 5.77GiB 112.22GiB
/mnt/disks/BackupSS/snaps/sspaces_daily_2018-07-29-070001
Look for example at snapshots from July 21st and 22nd, total used
space went from 199 to 277GiB, this is mostly from new added files, as
I confirmed from browsing those snapshots, there were no changes on
the 23rd, and a lot of files were deleted before the 24th, so should't
there be about 80GiB of exclusive content for the 22nd, or am I
misunderstanding how this is reported? ? Those were new files only,
never existed on previous snapshots, If I delete both snapshots from
the 22nd and the 23rd I expect to get about 80GiB freed space.
kernel 4.14.49 / btrfs-progs v4.15.1
Label: none uuid: e12ba68e-1200-467c-99e7-95e986c1d6f2
Total devices 2 FS bytes used 1.43TiB
devid 2 size 1.82TiB used 1.38TiB path /dev/sdh1
devid 3 size 931.51GiB used 706.51GiB path /dev/sdi1
Data, single: total=2.06TiB, used=1.43TiB
System, RAID1: total=32.00MiB, used=336.00KiB
Metadata, RAID1: total=4.00GiB, used=1.55GiB
GlobalReserve, single: total=512.00MiB, used=0.00B
