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Re: 4k sector drives

To: Michael Monnerie <michael.monnerie@xxxxxxxxxxxxxxxxxxx>
Subject: Re: 4k sector drives
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Fri, 23 Jul 2010 05:58:32 -0400
Cc: xfs@xxxxxxxxxxx
In-reply-to: <201007230809.28111@xxxxxx>
References: <201007211333.48363.eye.of.the.8eholder@xxxxxxxxx> <201007230809.28111@xxxxxx>
User-agent: Mutt/1.5.20 (2009-08-17)
On Fri, Jul 23, 2010 at 08:09:27AM +0200, Michael Monnerie wrote:
> On Mittwoch, 21. Juli 2010 Khelben Blackstaff wrote:
> > Nevertheless, you don't have to get them to report 4k to linux. As
> >  long as you align the partitions its fine. As i said in the other
> >  post, newer fdisk doesn't use "DOS compatibility mode" and uses
> >  sectors by default (instead of stupid CHS) with a 1MB alignment, so
> >  every partition will be properly aligned. If you don't dual boot
> >  Windows, you can also use GPT partitioning scheme. Also, from what i
> >  have seen, xfsprogs are quite clever and find most stuff on their
> >  own. I usually mkfs with "-s size=4096" just to be sure.
> 
> I always do -b size=4096 anyway, so I'm fine here. And I created the 
> partitions starting sector 512, so that should be good also.

-b size=4096 is the default anyway, for 4k sector drivers you also want
-s size=4096, which you do not want for 512 byte sector disks.

What values do the files

        /sys/block/<device>/queue/logical_block_size
        /sys/block/<device>/queue/physical_block_size
        /sys/block/<device>/alignment_offset

say about your disk?


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