linux-kernel - Re: ATA 4 KiB sector issues.

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Message-Id: <201003112030.44605.knikanth@suse.de>
Date:	Thu, 11 Mar 2010 20:30:44 +0530
From:	Nikanth Karthikesan <knikanth@...e.de>
To:	Theodore Tso <tytso@....edu>
Cc:	Damian Lukowski <damian@....rwth-aachen.de>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	Jeff Garzik <jeff@...zik.org>, Matthew Wilcox <matthew@....cx>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	James Bottomley <James.Bottomley@...e.de>,
	Tejun Heo <tj@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
	Daniel Taylor <Daniel.Taylor@....com>,
	Mark Lord <kernel@...savvy.com>,
	"H. Peter Anvin" <hpa@...or.com>, hirofumi@...l.parknet.co.jp,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, irtiger@...il.com,
	aschnell@...e.de, jdelvare@...e.de
Subject: Re: ATA 4 KiB sector issues.

On Thursday 11 March 2010 19:58:11 Theodore Tso wrote:
> On Mar 11, 2010, at 8:57 AM, Nikanth Karthikesan wrote:
> > I guess, what he meant was, to keep filesystem blocks aligned, even if
> > the partition is not. Say if the partition is mis-aligned by 512-bytes,
> > let the filesystem waste 4k-512bytes and keep it's blocks aligned. But it
> > might be a case of over-engineering, possibly requiring disk format
> > change.
> 
> Ah, yes, I agree with you; that's probably what he meant.
> 
> Sure, that's theoretically possible, but it would mean changing every
>  single filesystem, and it would require a file system format change --- or
>  at least a file system format extension.
> 
> It would seem to be way easier to simply fix the partitioning tools to do
>  the right thing, though.
> 

Yes. May be, just a simple but transparent device-mapper like mapping on top 
of the mis-aligned partition, to do the alignment. Then the file-system code 
need not change much.

But Linux already has device-mapper and Linux will not be affected with mis-
aligned partitions, when we use LVM.

But the actual problem here is that partitioning tools might create partitions 
that wont allow other operating-systems to boot. So it might be enough, if the 
partitioning tools just create partitions with (mis-)alignment requirement for 
Windows.

Thanks
Nikanth
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