Date: Sun, 29 Jun 2003 14:28:07 +0100
From: Jamie Lokier <jamie@shareable.org>
To: John Bradford <john@grabjohn.com>
Cc: linux-kernel@vger.kernel.org, mlmoser@comcast.net
Subject: Re: File System conversion -- ideas
Message-ID: <20030629132807.GA25170@mail.jlokier.co.uk>
References: <200306291011.h5TABQXB000391@81-2-122-30.bradfords.org.uk>
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John Bradford wrote:
I think
> the performance of an on-the-fly filesystem conversion utility is
> going to be so much worse than just creating a new partition and
> copying the data across,

which is awfully difficult if you have, say, a 60GB filesystem, a 60GB
disk, and nothing else.

> that the only reason to do it would be if you
> could do it on a read-write filesystem without unmounting it.

IMHO even if it requires the filesystem to be unmounted, it would
still be useful.  More challenging to use - you'd have to boot and run
from ramdisk, but much more useful than not being able to convert at all.

> What I'd like to see is union mounts which allowed you to mount a new
> filesystem of a different type over the original one, and have all new
> writes go to the new fileystem.  I.E. as files were modified, they
> would be re-written to the new FS.  That would be one way of avoiding
> the performance hit on a busy server.

But useless unless you have a second disk lying around that you don't
use for anything but filesystem conversions.

-- Jamie
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