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XFS and btrfs filesystem


Whilst reading the lesson on the above, the following questions/observations came to mind:
1. what's the difference between a snapshot and a backup -- or are the terms interchangeable; my understanding is that the former is a lot quicker to complete, so if they are different, can I do a snapshot and just use it as my backup?
2. are the commands xfsdump and xfsrestore snapshot-related commands? The man page describes them as "incremental" which implies the snapshot process...

In terms of readability, the warning text on the btrfs page reads:
btrfs was removed... it is not recommended to use an important filesystem...

I think that should either read:
...it is not recommended to use an imported filesystem...
...it is not recommended to use as an important filesystem...

Thoughts, anyone?


  • coop
    coop Posts: 915

    The expression "snapshot" means something you can easily revert to, reset the system to. A "backup" does not have this property although it will have all the data to do so, and some forms of backup are indeed images that can be dropped in just like a snapshot. But they are not logically the same.

    xfsdump and xfsrestore are, I believe, commands to restore backups, not snapshots, and the restore has a lot of options about what can be deleted, ignored etc. I've never used the commands and the man pages are not crystal clear :)

    Yes the word "as" is missing (your second choice) (use as an important filesystem)

  • fcioanca
    fcioanca Posts: 1,969

    This has been updated in the course. Thank you for flagging it.

  • cfuchs
    cfuchs Posts: 15
    edited January 2022

    Re 1.

    • in my understanding (as a btrfs user), a snapshot shares the physical media of the original (and may to a large extend even overlap with the original), a backup is separate (either just duplicated on the same physical media, or on remote media).
    • so a snapshot is purely logical (not guaranteed to have any separate space in the physical world), while a backup is physical (guaranteed to occupy a different space in the physical world - even if it is only a separate portion of the physical carrier).


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