On 1/23/06, Kyle Moffett <[email protected]> wrote:
> On Jan 23, 2006, at 02:24, Theodore Ts'o wrote:
> > Hot-shrinking a filesystem is certainly possible for any
> > filesystem, but the problem is how many filesystem data structures
> > you have to walk in order to find all the owner of all of the
> > blocks that you have to relocate. That generally isn't a RAM
> > overhead problem, but the fact that in general, most filesystems
> > don't have an efficient way to answer the question, "who owns this
> > arbitrary disk block?" Having extents means you have a slightly
> > more efficient encoding system, but it still is the case that you
> > have to check potentially every file in the filesystem to see if it
> > is the owner of one of the disk blocks that needs to be moved when
> > you are shrinking the filesystem.
>
> The way that I'm considering implementing this is by intentionally
> fragmenting the allocation bitmap, catalog file, etc, such that each
> 1/8 or so of the disk contains its own allocation bitmap describing
> its contents, its own set of files or directories, etc. The
> allocator would largely try to keep individual btree fragments
> cohesive, such that one of the 1/8th divisions of the disk would only
> have pertinent data for itself. The idea would be that when trying
> to look up an allocation block, in the common case you need only
> parse a much smaller subsection of the disk structures.
this sounds exactly the same as ext2/ext3 allocation groups :)
> > And the only use for such a [reverse-mapping] data structure would
> > be to make shrinking a filesystem more efficient.
>
> Not entirely true. I _believe_ you could use such data structures to
> make the allocation algorithm much more robust against fragmentation
> if you record the right kind of information.
>
> Cheers,
> Kyle Moffett
>
> --
> If you don't believe that a case based on [nothing] could potentially
> drag on in court for _years_, then you have no business playing with
> the legal system at all.
> -- Rob Landley
>
--
Greetz, Antonio Vargas aka winden of network
http://wind.codepixel.com/
[email protected]
[email protected]
Every day, every year
you have to work
you have to study
you have to scene.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
