[linux-lvm] LVM onFly features
Marc-Jano Knopp
pub_ml_lvm at marc-jano.de
Sat Dec 10 20:22:32 UTC 2005
On Sat, 10 Dec 2005 at 13:14 (-0700), Michael Loftis wrote:
> --On December 10, 2005 9:06:46 PM +0100 Marc-Jano Knopp <pub_ml_lvm at marc-jano.de> wrote:
> >On Sat, 10 Dec 2005 at 13:03 (-0700), Michael Loftis wrote:
> >>--On December 10, 2005 8:48:27 PM +0100 Marc-Jano Knopp
> >><pub_ml_lvm at marc-jano.de> wrote:
> >>> On Sat, 10 Dec 2005 at 14:38 (-0500), Mag Gam wrote:
[Resizing of file systems]
[...]
> ReiserFS has hot expansion capabilities, but no (yet?) hot shrinking
> capabilities. One of the reasons it has these features and ext2/3 does not
> is because ext2/3 are very old filesystems designed on a different
> mentality of a static filesystem. On-line expansion of ext2 based
> filesystems is an extremely complicated venture, it might honestly even be
> impossible.
>
> ReiserFS has the advantage here because it doesn't necessarily pre-write
> out a lot of filesystem meta-information (superblocks, inodes, bitmaps,
> etc), instead these structures are entirely dynamic to begin with, so
> enlarging them at runtime is trivial, requires a very short lock and a
> change to a few numbers. Ext2 resizing requires actually rewriting a lot
> of filesystem metadata.
Thanks for the detailled explanation!
Yes, I would *love* to use a totally new file system with a new,
dynamic, good design, but - just as many others - had my experiences
with ReiserFS and it will take a *lot* of time for ReiserFS to restore
confidence. So for now, I'll probably stay with ext3, with which I had
no problems so far.
JFS/XFS should also both be capable of growing, XFS of online-growth,
IIRC.
Gruß
Marc-Jano
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