linux-kernel - Re: BTRFS partition usage...

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Date:	Wed, 13 Feb 2008 00:39:16 +0100 (CET)
From:	Jan Engelhardt <jengelh@...putergmbh.de>
To:	David Miller <davem@...emloft.net>
cc:	chris.mason@...cle.com, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, btrfs-devel@....oracle.com
Subject: Re: BTRFS partition usage...


On Feb 12 2008 15:26, David Miller wrote:
>
>> (Yes, I had xfs on sparc before, so it's not like you NEED the 
>> whitespace at the start of a partition.)
>
>You actully do unless you want to lose significant chunks of your disk
>space.
>
>The Sun disk label only allows you to specify the start of a partition
>in cylinders, so if you want to use a filesystem like XFS you have to
>start the partition on cylinder 1 which can be many blocks into the
>disk.  That entire first cylinder is completely wasted.

Ok you do have a point there. The GPT users win of course, since it
uses LBA, not cyls, so the number of lost bytes is generally below
a cyl.
On the other hand, the H and S of CHS could be lowered and S increased,
e.g. divide H by 2, divide S by 2, multiply S by 4. This gives a finer
bytes/cylinder granularity.

>What XFS does by putting the superblock at zero is simply does not
>take these kinds of issues into consideration.
>

Well it was designed for a different system initially with
a different style of booting.
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