* Re: questions about io scheduler
[not found] ` <1wxyd-1WX-1@gated-at.bofh.it>
@ 2004-03-09 20:22 ` Bill Davidsen
0 siblings, 0 replies; 7+ messages in thread
From: Bill Davidsen @ 2004-03-09 20:22 UTC (permalink / raw)
To: Mike Fedyk; +Cc: Linux Kernel Mailing List
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...
^ permalink raw reply [flat|nested] 7+ messages in thread
* questions about io scheduler
@ 2004-03-05 9:22 Kyle Wong
2004-03-05 9:20 ` Nick Piggin
2004-03-05 9:20 ` Jens Axboe
0 siblings, 2 replies; 7+ messages in thread
From: Kyle Wong @ 2004-03-05 9:22 UTC (permalink / raw)
To: linux-kernel
1. Is anticipatory io scheduler + echo 0 >
/sys/block/hd*/queue/iosched/antic_expire = deadline scheduler?
2. Does io scheduler works with md RAID? Correct me if I'm wrong,
io-schedular <--> md driver <--> harddisks.
Regards,
Kyle
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: questions about io scheduler
2004-03-05 9:22 Kyle Wong
@ 2004-03-05 9:20 ` Nick Piggin
2004-03-05 22:57 ` Mike Fedyk
2004-03-05 9:20 ` Jens Axboe
1 sibling, 1 reply; 7+ messages in thread
From: Nick Piggin @ 2004-03-05 9:20 UTC (permalink / raw)
To: Kyle Wong; +Cc: linux-kernel
Kyle Wong wrote:
>1. Is anticipatory io scheduler + echo 0 >
>/sys/block/hd*/queue/iosched/antic_expire = deadline scheduler?
>
>
It is very similar but not quite the same.
>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.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: questions about io scheduler
2004-03-05 9:20 ` Nick Piggin
@ 2004-03-05 22:57 ` Mike Fedyk
2004-03-05 23:49 ` Timothy Miller
0 siblings, 1 reply; 7+ messages in thread
From: Mike Fedyk @ 2004-03-05 22:57 UTC (permalink / raw)
To: Nick Piggin; +Cc: Kyle Wong, linux-kernel
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.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: questions about io scheduler
2004-03-05 22:57 ` Mike Fedyk
@ 2004-03-05 23:49 ` Timothy Miller
2004-03-05 23:58 ` Mike Fedyk
0 siblings, 1 reply; 7+ messages in thread
From: Timothy Miller @ 2004-03-05 23:49 UTC (permalink / raw)
To: Mike Fedyk; +Cc: Nick Piggin, Kyle Wong, linux-kernel
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?
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: questions about io scheduler
2004-03-05 23:49 ` Timothy Miller
@ 2004-03-05 23:58 ` Mike Fedyk
0 siblings, 0 replies; 7+ messages in thread
From: Mike Fedyk @ 2004-03-05 23:58 UTC (permalink / raw)
To: Timothy Miller; +Cc: Nick Piggin, Kyle Wong, linux-kernel
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.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: questions about io scheduler
2004-03-05 9:22 Kyle Wong
2004-03-05 9:20 ` Nick Piggin
@ 2004-03-05 9:20 ` Jens Axboe
1 sibling, 0 replies; 7+ messages in thread
From: Jens Axboe @ 2004-03-05 9:20 UTC (permalink / raw)
To: Kyle Wong; +Cc: linux-kernel
On Fri, Mar 05 2004, Kyle Wong wrote:
> 1. Is anticipatory io scheduler + echo 0 >
> /sys/block/hd*/queue/iosched/antic_expire = deadline scheduler?
It isn't 100% the same, but very very close.
> 2. Does io scheduler works with md RAID? Correct me if I'm wrong,
> io-schedular <--> md driver <--> harddisks.
No, it's md -> io scheduler -> hard drive.
--
Jens Axboe
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2004-03-09 20:17 UTC | newest]
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[not found] ` <1wxyd-1WX-1@gated-at.bofh.it>
2004-03-09 20:22 ` questions about io scheduler Bill Davidsen
2004-03-05 9:22 Kyle Wong
2004-03-05 9:20 ` Nick Piggin
2004-03-05 22:57 ` Mike Fedyk
2004-03-05 23:49 ` Timothy Miller
2004-03-05 23:58 ` Mike Fedyk
2004-03-05 9:20 ` Jens Axboe
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