Unioning file systems: Architecture, features, and design choices [LWN.net]

Unioning file systems: Architecture, features, and design choices

Posted Mar 20, 2009 14:37 UTC (Fri) by masoncl (subscriber, #47138)
In reply to: Unioning file systems: Architecture, features, and design choices by vaurora
Parent article: Unioning file systems: Architecture, features, and design choices

I'm afraid the btrfs image on the dvd is the only way other than the existing union filesystems. The same goes for the unionfs use cases around network filesystems.

One problem with that is btrfs likes to leave free space hanging around, and so it isn't yet well suited to compacting images down on an iso/dvd.

Patching btrfs progs to create a compact btrfs FS for burning would be a fun project if anyone is looking for ways to fill their time ;)

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Unioning file systems: Architecture, features, and design choices

Posted Mar 20, 2009 17:26 UTC (Fri) by arnd (subscriber, #8866) [Link]

To take this thought a little bit further, this could also incorporate:

* laying out files and metadata for performance characteristics of optical
media (seek times vary a lot with location, 2kb sector boundary, ...).

* compressing all files in advance may give you much better placement
options than online compression.

* This could be integrated into mkisofs in the same way that HFS support
is. Iso9660 leaves a significant amount of free space in the front, so it
may just fit.

* In a similar way, it could be done in the same way that ext3 conversion
works, but on an existing iso9660 file system to create a hybrid file
system. Bonus points for making it work with multisession writing on an
already burnt iso9660 disk.