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Re: ATA 4 KiB sector issues.

From:  "Martin K. Petersen" <martin.petersen-AT-oracle.com>
To:  Tejun Heo <tj-AT-kernel.org>
Subject:  Re: ATA 4 KiB sector issues.
Date:  Mon, 08 Mar 2010 10:18:27 -0500
Cc:  "linux-ide-AT-vger.kernel.org" <linux-ide-AT-vger.kernel.org>, lkml <linux-kernel-AT-vger.kernel.org>, Daniel Taylor <Daniel.Taylor-AT-wdc.com>, Jeff Garzik <jeff-AT-garzik.org>, Mark Lord <kernel-AT-teksavvy.com>, tytso-AT-mit.edu, "H. Peter Anvin" <hpa-AT-zytor.com>, hirofumi-AT-mail.parknet.co.jp, Andrew Morton <akpm-AT-linux-foundation.org>, Alan Cox <alan-AT-lxorguk.ukuu.org.uk>, irtiger-AT-gmail.com, Matthew Wilcox <matthew-AT-wil.cx>, aschnell-AT-suse.de, knikanth-AT-suse.de, jdelvare-AT-suse.de, Karel Zak <kzak-AT-redhat.com>, Jim Meyering <jim-AT-meyering.net>
Archive-link:  Article, Thread

>>>>> "Tejun" == Tejun Heo <tj@kernel.org> writes:

Tejun> The [Windows Vista/7] partitioner seems to be using 1M as the
Tejun> basic alignment unit and offsetting from there if explicitly
Tejun> requested by the drive

Yep.


Tejun> Please note that hdparm is misreporting the alignment offset.  It
Tejun> should be reporting 512 instead of 256 for offset-by-one drives.

Already fixed.  Your hdparm must be old.



Tejun> Partitioners maybe should only align partitions which will be
Tejun> used by Linux and default to the traditional layout for others
Tejun> while allowing explicit override.

I don't think we take the partition type into account.  Karel?


Tejun> Reportedly, commonly used partitioners aren't ready to handle
Tejun> drives larger than 2 TiB in any configuration and alignment isn't
Tejun> done properly for drives with 4 KiB physical sectors.  4 KiB
Tejun> logical sector support is broken in both the kernel 

Huh, what?  My homedir is on a 4KiB LBS/PBS drive and has been for ~2
years.


Tejun> (need more details and probably a whole section on partitioner
Tejun> behaviors)

I'm Cc:'ing Karel Zak and Jim Meyering who have been doing all the
alignment work for fdisk and parted respectively.  Karel, Jim: The full
writeup is here:

	http://ata.wiki.kernel.org/index.php/ATA_4_KiB_sector_issues

It'd be great if you guys could share what you have been doing to the
tooling.


Tejun> Unfortunately, the transition to 4 KiB sector size, physical only
Tejun> or logical too, is looking fairly ugly.  Hopefully, a reasonable
Tejun> solution can be reached in not too distant future but even with
Tejun> all the software side updated, it looks like it's gonna cause
Tejun> significant amount of confusion and frustration.

With regards to XP compatibility I don't think we should go too much out
of our way to accommodate it.  XP has been disowned by its master and I
think virtualization will take care of the rest.

FWIW, recent fdisk has a command line flag that will enable/disable DOS
compatible layout.

-- 
Martin K. Petersen	Oracle Linux Engineering
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