Message-ID: <4B4AD2CE.8040207@zytor.com>
Date: Sun, 10 Jan 2010 23:27:10 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: "Martin K. Petersen" <martin.petersen@oracle.com>
CC: Andreas Dilger <adilger@sun.com>, Karel Zak <kzak@redhat.com>,
       linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
       util-linux-ng@vger.kernel.org
Subject: Re: [ANNOUNCE] util-linux-ng v2.17 (stable)
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On 01/10/2010 10:36 PM, Martin K. Petersen wrote:
>>>>>> "Andreas" == Andreas Dilger <adilger@sun.com> writes:
> 
> Andreas> I agree whole heartedly.  We steer users very sharply away from
> Andreas> using partitions at all, because on h/w RAID devices the
> Andreas> 512-byte offset from fdisk completely kills RAID-5/6
> Andreas> performance.
> 
> I don't have a problem aligning to 1MB (taking alignment_offset into
> account) by default but there needs to be an easy override.  There are
> RAID arrays that internally compensate for the legacy 63 sector offset
> and we'll cause misalignment if we start at 1MB on those.
> 
> I'm heavily lobbying our storage partners to make sure they fill out the
> right SCSI bits if their LUNs are not naturally aligned.  But there are
> obviously going to be legacy devices out there that will need manual
> alignment compensation.
> 

Yes, but we shouldn't default to braindead mode.

	-hpa

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

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