Re: XFS and journalling filesystems

Jeremy Fitzhardinge (jeremy@goop.org)
Sun, 30 May 1999 12:02:51 -0700 (PDT)


On 28-May-99 Adam Lock wrote:
> I was just browsing the BeOS site and that too claims to have a 64-bit
> journalling filesystem. Perhaps that would be better suited for home systems
> if
> only there were more details available for it...

More has been published about bfs than almost any other commercial filesystem.
There's a book ("Practial File System Design with the Be file system") which
goes into great detail about it. There's also one read-only implementation of
a driver for Linux.

The Be filesystem is pretty good. It's basically a traditional structure,
except directories are btrees and there's a metadata journal. There's a number
of interesting BeOS-specific features too, such as indexed file attributes.

It does have some limitations. Block mapping is done with the normal
single/double (no triple) indirect blocks, which contain extents. The maximum
file size is about 34G on an unfragmented filesystem. The block mapping
imposes a maximum number of extents, which means the max file size goes down as
the disk fragments.

It has definitely been designed as a single-user desktop filesystem. There's a
number of tradeoffs which have been made against servers and towards
single-user use, which makes sense given the nature of the OS.

J

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