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Message-ID: <4C4994CB.2050200@hardwarefreak.com>
Date: Fri, 23 Jul 2010 08:10:35 -0500
From: Stan Hoeppner <stan@hardwarefreak.com>
MIME-Version: 1.0
Subject: Re: 4k sector drives
References: <201007211333.48363.eye.of.the.8eholder@gmail.com>	<201007230809.28111@zmi.at>
	<20100723095832.GA23174@infradead.org> <201007231259.11714@zmi.at>
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Michael Monnerie put forth on 7/23/2010 5:59 AM:
> On Freitag, 23. Juli 2010 Christoph Hellwig wrote:
>> -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.
> 
> Thanks for clarification. Should I use "-s size=4096" despite the drive 
> saying 512b sectors? It's a "hidden" 4K sector drive, so maybe declaring 
> it extra for XFS helps performance? Or does it not matter at all?
>  
>> 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?
> 
> 512, 512, 0 for a Western Digital D20EARS-00MVWB0 (2TB) which has 4K 
> sectors but obviously hides it.

The WD20EARS-00MVWB0 is definitely a 4k sector drive:
http://products.wdc.com/Library/Flyer/ENG/2178-771123.pdf

If you're currently seeing somewhere between 60-120MB/s per drive with hdparm
or dd then you don't need to further tweak anything.  If alignment is off,
from all I've read, performance will be abysmal, down in the sub 30MB/s range.

-- 
Stan

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