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Date: Fri, 08 Jan 2010 15:40:33 -0700
From: Andreas Dilger <adilger@sun.com>
Subject: Re: [ANNOUNCE] util-linux-ng v2.17 (stable)
In-reply-to: <4B47A713.9060405@zytor.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Karel Zak <kzak@redhat.com>, linux-kernel@vger.kernel.org,
       linux-fsdevel@vger.kernel.org, util-linux-ng@vger.kernel.org
Message-id: <329167C1-CF54-4742-B0B7-AD0B9DEFDEC1@sun.com>
References: <20100108093302.GS1969@nb.net.home> <4B47A713.9060405@zytor.com>
Sender: linux-kernel-owner@vger.kernel.org
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On 2010-01-08, at 14:43, H. Peter Anvin wrote:
> On 01/08/2010 01:33 AM, Karel Zak wrote:
>> fdisk:
>>   - the fdisk command aligns newly created partitions to  
>> minimum_io_size
>>     boundary ("minimum_io_size" is physical sector size or stripe  
>> chunk
>>     size on RAIDs).
>>
>>   - the fdisk command supports disks with alignment_offset now.
>
> I think we should align, by default, much more aggressively than  
> that --
> because frequently we just don't know what the real physical alignment
> is (think of flash media, which uses large erase blocks underneath.)
> Windows aligns partitions 1 MB boundaries by default now -- I think
> that's probably a reasonably good idea, at least for any disk that's  
> not
> tiny, say 256 MB or less.

I agree whole heartedly.  We steer users very sharply away from using  
partitions at all, because on h/w RAID devices the 512-byte offset  
from fdisk completely kills RAID-5/6 performance.

Making the default minimum alignment for DOS/GPT partitions makes a  
lot of sense, and LVM PEs should be on 1MB boundaries as well (I don't  
think that is the case today either).


Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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