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

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Date:	Wed, 10 Mar 2010 03:22:59 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Johannes Stezenbach <js@...21.net>
CC:	Greg Freemyer <greg.freemyer@...il.com>,
	James Bottomley <James.Bottomley@...e.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, mkp@....net
Subject: Re: ATA 4 KiB sector issues.

On 03/10/2010 02:46 AM, Johannes Stezenbach wrote:
> On Tue, Mar 09, 2010 at 04:32:04PM -0800, H. Peter Anvin wrote:
>>
>> It can.  The BIOS doesn't care about the partition table at all --
>> all it does is load the MBR.
>
> A little story for your entertainment pleasure:
>
> I have a Gigabyte GA-MA78GM-S2H board, and during install
> turned off the power after partitioning but before formatting
> any partition because I got distracted by something else.
>
> Result: System could not boot anymore, BIOS hung before
> I could get to the "select boot device" screen. This also
> happened when I removed the hdd from the boot device
> list in BIOS. The last BIOS message was "Verifying DMI Pool Data"
> and you can find numerous similar reports by searching for
> 'gigabyte bios hang "Verifying DMI Pool Data"'.
>
> In my case it worked to switch the SATA mode from AHCI to
> something else, then wipe the partition table and switch
> back to AHCI.  But I read on the net that some people had
> to format the drive in another PC, or hotplug it after the BIOS
> got past "Verifying DMI Pool Data".
>

Well, yes, there are buggy BIOSes of a gazillion varieties.  A fair 
number of them read the partition table to try to guess what C/H/S 
geometry the user intended.  However, the GPT spec specifically uses a 
"Protective MBR" to guard against this and other issues like it; it 
makes the entire disk look to MBR-reading software like a single fully 
partitioned disk with one large partition on it.

	-hpa
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