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
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
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.
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.
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?
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.
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...