5 ms·

1) Yes, it's copy on write, and requires such support from the underlying filesystem (Btrfs, maybe XFS not sure of what others support it) 2) It's intended to

1) Yes, it's copy on write, and requires such support from the underlying filesystem (Btrfs, maybe XFS not sure of what others support it) 2) It's intended to be treated 100% as if it had been copied the classical way. It's not a hardlink or a symlink and can be treated as a completely new file

cmurf 7y ago
Support for reflinks in XFS for a while now, although it requires a mkfs time option to enable it. That option was just enabled by default in xfsprogs-5.1.0 which is now in Fedora 31 (still prerelease).
- simcop2387 7y ago
  Yea my memory was fuzzy and I knew it was planned and being worked on but couldn't remember if it had happened yet. I think F2FS and bcachefs are also supposed to support it but I'm not sure about their level of support either.
- zepearl 7y ago
  Cool => I'll then probably reformat on my root server the partition hosting the images of my VMs from EXT4 to XFS => then to make 100% backups from time to time I would just have to shut them down for a minute, do a "cp --reflink" of their image-file on the host/dom0, then I could start them up again and do anytime later the slow download of their "copied" file. Any recommendations about a utility (working on a layer higher than the filesystem) that can synchronize only the chunks of a specific file that has changed since the last sync and which generates as final result a "normal" file (no behind-the-curtains database - just copy the identical data from the local/old file and the changes/new data from the remote location to get a normal up-to-date local file)?
  - caf 7y ago
    I believe rsync is the utility you are looking for.
    - zepearl 7y ago
      Damn, now I'm ashamed of myself - it's since forever that I'm using rsync... :) I think that when I tested this with rsync a long time back I did a similar mistake like this one https://stackoverflow.com/questions/28819379/block-level-copying-and-rsync https://stackoverflow.com/questions/28819379/block-level-cop... (doing a sync not over a network) and/or this one https://www.reddit.com/r/linux/comments/3nhx0p/rsync_block_level_incremental_backup/ https://www.reddit.com/r/linux/comments/3nhx0p/rsync_block_l... (doing a sync by adding/removing some bytes instead of just changing their values, as it would happen in the preallocated img-file of the VMs). I'll test it again - thanks a lot for the info!!

cmurf 7y ago

Support for reflinks in XFS for a while now, although it requires a mkfs time option to enable it. That option was just enabled by default in xfsprogs-5.1.0 which is now in Fedora 31 (still prerelease).

simcop2387 7y ago
Yea my memory was fuzzy and I knew it was planned and being worked on but couldn't remember if it had happened yet. I think F2FS and bcachefs are also supposed to support it but I'm not sure about their level of support either.
zepearl 7y ago
Cool => I'll then probably reformat on my root server the partition hosting the images of my VMs from EXT4 to XFS => then to make 100% backups from time to time I would just have to shut them down for a minute, do a "cp --reflink" of their image-file on the host/dom0, then I could start them up again and do anytime later the slow download of their "copied" file. Any recommendations about a utility (working on a layer higher than the filesystem) that can synchronize only the chunks of a specific file that has changed since the last sync and which generates as final result a "normal" file (no behind-the-curtains database - just copy the identical data from the local/old file and the changes/new data from the remote location to get a normal up-to-date local file)?
- caf 7y ago
  I believe rsync is the utility you are looking for.
  - zepearl 7y ago
    Damn, now I'm ashamed of myself - it's since forever that I'm using rsync... :) I think that when I tested this with rsync a long time back I did a similar mistake like this one https://stackoverflow.com/questions/28819379/block-level-copying-and-rsync https://stackoverflow.com/questions/28819379/block-level-cop... (doing a sync not over a network) and/or this one https://www.reddit.com/r/linux/comments/3nhx0p/rsync_block_level_incremental_backup/ https://www.reddit.com/r/linux/comments/3nhx0p/rsync_block_l... (doing a sync by adding/removing some bytes instead of just changing their values, as it would happen in the preallocated img-file of the VMs). I'll test it again - thanks a lot for the info!!