Am 19.02.2024 um 04:20 schrieb Keith Bainbridge: > I am convinced that the missing space is used by btrfs snapshot process.
First off: I am not a btrfs user (and will never be, i might add). I am using zfs since many years, and - although i read an awful lot of documentation beforehand, and played around with it quite a bit, i had to learn a couple of lessons "the hard way". To me, what i am inferring from your mails, are a couple of conceptual misundestandings of what a COW-filesystem is, and how to best make use of it. Especially the time-machine using snapshots and hardlinks seems very kinky to me. I am using zfs somewhat in a similar way, but it took me some years to set it up in a good way. Apart from a warning and the usual RTFM, i do not have much to offer. Except maybe for this: Snapshots hold space, they are not like hardlinks. (although one can snapshot hardlinks ;-) ) Once, some older filesystem state is snapshotted, its space is taken until the snapshot gets destroyed/removed. This can lead to situations, where a device is full, but in order to free some space, deleting files will NOT help, because in order to do so, a change in the directory needs to be made, but there may not be the room to create a copy of it in the first place. And deleting files from a snapshot is not feasable (at least not in zfs). To my eyes, your handling of the system looks somewhat risky and not well planned. You may go on this way, as long as you consider the whole thing as being part of a longish learning session. But do not trust important data being safe this way! just my 2 cents
