Date: Sun, 29 Jun 2003 17:24:47 +0100
From: John Bradford <john@grabjohn.com>
Message-Id: <200306291624.h5TGOl4A001008@81-2-122-30.bradfords.org.uk>
To: linux-kernel@vger.kernel.org, thervoy@post.pl
Subject: Re: File System conversion -- ideas
Cc: jamie@shareable.org, john@grabjohn.com, mlmoser@comcast.net
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1431
Lines: 44

> > 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.
> >
>
> I think that filesystem conversion on-the-fly is useless. Why? If you're
> making conversion of filesystem, you have to make good backup of data
> from that filesystem.

I agree.

Imagine a webserver with all it's webpages on a 40 GB EXT-2 partition
on /dev/sda1.

If I wanted to move the data on to a ReiserFS partition, I would just:

* Create the new partition on another device, E.G. /dev/sdb1
* Mount /dev/sda1 read-only
* Copy the data across to /dev/sdb1 as a nice process
* Stop the webserver processes
* Unmount /dev/sda1
* Mount /dev/sdb1 read-only
* Restart the webserver processes
* Test it
* Mount /dev/sdb1 read-write
* Keep /dev/sda1 around as a quick-to-access backup until I was sure
  it was all working correctly.
* Re-use /dev/sda1

The webserver would be off-line for only a few seconds, and
performance would not be significantly degraded at any time.

John.
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