Message-ID: <40491414.2060404@matchmail.com>
Date: Fri, 05 Mar 2004 15:58:12 -0800
From: Mike Fedyk <mfedyk@matchmail.com>
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To: Timothy Miller <miller@techsource.com>
CC: Nick Piggin <piggin@cyberone.com.au>, Kyle Wong <kylewong@southa.com>,
       linux-kernel@vger.kernel.org
Subject: Re: questions about io scheduler
References: <088201c40293$5b27ce80$9c02a8c0@southa.com> <40484643.7070104@cyberone.com.au> <404905E1.70709@matchmail.com> <4049121D.1060405@techsource.com>
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Timothy Miller wrote:
> 
> 
> Mike Fedyk wrote:
> 
>> Nick Piggin wrote:
>>
>>>
>>>
>>> Kyle Wong wrote:
>>>
>>>> 2. Does io scheduler works with md RAID? Correct me if I'm wrong,
>>>> io-schedular <-->  md driver <--> harddisks.
>>>>
>>>>
>>>
>>> It goes md driver -> io schedulers -> hard disks.
>>
>>
>>
>> There is an IO scheduler per disk.
>>
>> So MD submits the data to each disk through the IO scheduler.
>>
>> This allows you to have the heads on each disk in the array at 
>> different locations, and helps keep response times lower for seeky loads.
> 
> 
> Say you've got a RAID1.  In this case, MD could send the read request to 
> either device.  How does it decide which one to use?

The one with the drive head closest to the data.
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