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timeshift with btrfs: am I doing it right?
(lemmy.kde.social)
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this post was submitted on 20 Jul 2023
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so it is a completely different process than with rsync... I always thought of the two ways are pretty similar
Copy on write is the difference. As I understand it, a btrfs snapshot takes no space when it's created (beyond the file system record). The filesystem is always writing changes to file chunks as a new copy of the chunk, which is then recorded as a replacement of the old chunk (which is still present on-disk). So a snapshot tracks all of these later changes, and the file system keeps the old file chunks preserved as long as you keep the snapshot. That's why you can mount a btrfs snapshot. It just shows you the volume through the lens of all of these saved changes.
When you delete a snapshot you are then marking these preserved chunks as free space. So that is also quick.
Whoever invented this is a genius, a genius...
thanks for the help!