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Re: XFS allows expansions, but no contraction?

To: Michael Best <mbest@xxxxxxxxxxxxx>
Subject: Re: XFS allows expansions, but no contraction?
From: Eric Sandeen <sandeen@xxxxxxx>
Date: 26 Sep 2002 15:32:56 -0500
Cc: linux-xfs@xxxxxxxxxxx
In-reply-to: <3D936DFA.5060900@emergence.com>
References: <3D936DFA.5060900@emergence.com>
Sender: linux-xfs-bounce@xxxxxxxxxxx
This has been discussed on the list before, and I -think- Steve detailed
the technical difficulties.  If you can't find it in the archives, I'll
post a summary.

-Eric

On Thu, 2002-09-26 at 15:28, Michael Best wrote:
> I know that XFS doesn't/didn't support filesystem resizing that involves
> making the filesystem smaller.
> 
> What are the technical hurdles faced if such a program were to be written?
> 
> Or would this be fairly obvious from reading the filesystem specification?
> 
> Just working from assumptions (perhaps wrong) would be that you would
> have to find all files/inodes that are contained in the space that you
> need to want to truncate from your filesystem.   Do some something
> similar to defragment/move those file into the non-truncated space.  And
> then rewrite the XFS "superblock"?
> 
> Is the biggest challenge then finding the files that are in this space?
> Telling the filesystem it is smaller? Moving/defragmenting the files?
> Due to limitations on how the code chooses where to write it's next
> blocks?  Having to sort all the files on the filesystem?
> 
> Just some random thoughts that came to me about resizing.  This would be
> a good thing for LVM if I remember, and I was more or less curious why
> there isn't a tool (and then assumed that there wasn't one because it
> was hard to do due to a design decision).
> 
> -Mike
> 
-- 
Eric Sandeen      XFS for Linux     http://oss.sgi.com/projects/xfs
sandeen@xxxxxxx   SGI, Inc.         651-683-3102


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