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SubjectRe: questions about io scheduler
Mike Fedyk wrote:
> 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.

Or hopefully the one not in use if one is busy...

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