100% disk usage on small disks

[Thomas Templin]

on a small disk (here 60GB ssd) apt-btrfs-snapshot does not check if there is enough disk-space left for a snapshot.

For novice Linux Users if a system hangs due to 100% disk usage this is at least a tremendous showstopper. For newbies the system reaches a unusable state if 100% disk space is used. If one doesn't know that it's due to apt-btrfs-snapshot this is a big pitfall.

There should be a check on the disk size and on the amount of free disk space before a snapshot is done. If the disk space is under a certain size apt-btrfs should ask if it is ok to delete the oldest snapshot(s).

[Rolf Leggewie (r0lf)]

Thomas, I believe something else is at play here.

Creating even a 100 Exabyte snapshot uses up almost no additional space. I create automatic snapshots every 10 minutes(!) for a btrfs that has only a 1GB (yes, GB not TB) internal flash drive (Igel thinclient) and that is filled 60%. I don't recommend doing this as it creates other problems, but they are not "100% disk usage".

That being said, it is especially bad to fill up a btrfs close to capacity as a btrfs needs room to breathe to operate properly.

Maybe https://btrfs.wiki.kernel.org/index.php/Problem_FAQ#I_get_.22No_space_left_on_device.22_errors.2C_but_df_says_I.27ve_got_lots_of_space is a good read for you to resolve the problem you were having.