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Re: [linux-lvm] LVM onFly features



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 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 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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