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

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Message-ID: <4B9E489F.6040709@zytor.com>
Date:	Mon, 15 Mar 2010 07:47:59 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Denys Vlasenko <vda.linux@...glemail.com>
CC:	david@...g.hm, Arnd Bergmann <arnd@...db.de>,
	Tejun Heo <tj@...nel.org>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Daniel Taylor <Daniel.Taylor@....com>,
	Jeff Garzik <jeff@...zik.org>, Mark Lord <kernel@...savvy.com>,
	tytso@....edu, hirofumi@...l.parknet.co.jp,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, irtiger@...il.com,
	Matthew Wilcox <matthew@....cx>, aschnell@...e.de,
	knikanth@...e.de, jdelvare@...e.de
Subject: Re: ATA 4 KiB sector issues.

On 03/15/2010 02:56 AM, Denys Vlasenko wrote:
> I think Linux already is doing this. The problem is, in many cases
> OS can't possibly do this, short of using a specially designed
> filesystem.
> 
> If you untar a Linux kernel source tarball on a seriously
> fragmented ext2 filesystem, there will be a lot of discontiguous
> and/or misaligned writes smaller than 256K.
> Only smart firmware can help in this case.

Yes, but guess what... there is a lot of stupid firmware out there, and
there are lots of RAID arrays, and so on.

"Seriously fragmented" means you have already lost in the first place.

This doesn't change the fact that this is a real issue and that that is
the major reason why aligning to 63*4K is a bad idea.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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