Date: Sun, 29 Jun 2003 19:37:54 +0100
From: John Bradford <john@grabjohn.com>
Message-Id: <200306291837.h5TIbsJi001136@81-2-122-30.bradfords.org.uk>
To: linux-kernel@vger.kernel.org, wowbagger@sktc.net
Subject: Re: File System conversion -- ideas
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2102
Lines: 48

> This is a place where logical volume management can help.
>
> For example, suppose you have a 60G disk, 55G of data, in ext2, and you 
> wish to convert to ReiserFS.
>
> Step 1: Shrink the volume to 55G. This requires a "shrink disk" utility 
> for the source file system (which exists for the major file systems in 
> use today).
> Step 2: Create an LVM block in the remaining 5G.
> Step 3: Create a ReiserFS in the LVM block.
> Step 4: Move 5G of data from the ext2 system to the ReiserFS block.
> Step 5: Shrink the ext2 volume by another 5G
> Step 6: Convert that 5G into an LVM block
> Step 7: Add that block to the ReiserFS volume group.
> Step 8: Grow the ReiserFS.
> Step 9: Repeat 4-8 as needed.
>
>
> This is why I'd really love to see LVM|EVM become standard, not just in 
> the kernel but in the distributions - if every distro by default made 
> all Linux volumes in LVM, then migrating data to bigger drives/adding 
> more space/converting file systems would be so much easier.

It's also a good reason not to use one huge partition on each disk,
and a good reason not to partition the whole disk when it's not
needed.

I've seen, (mainly desktop, not server), Linux machines with one
physical disk containing two partitions, root and swap, with the swap
partition being twice the physical memory of the box, even when the
box has more than a gigabyte of physical RAM.

It's usually more flexible just to partition the space you need, and
add more partitions when necessary.  For typical desktop use, swap
isn't even necessary with 1 GB of physical RAM.

For example, if you have an 80 GB disk, you could initially partition
10 GB for the root partition, and leave 70 GB unused.  When the root
partition fills us, you can simply use du -s /* to see which
directories are taking up the most space, and move them to separate
partitions.

John.
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