Why all raid devices do have zero 'time in queue' value?
 

Good day.

I've look to stat for all MD devices I have (raid0, raid1, raid10) - all
of them reports 0 for time_in_queue field in /sys/block/mdX/stat file.


Is any reason why all raid devices contains no information about time
spent on requests processing?


Thanks.

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Why all raid devices do have zero 'time in queue' value?
 

On Sun, 11 Mar 2012 02:33:34 +0400 George Shuklin <george.shuklin@gmail.com>
wrote:

> Good day.
>
> I've look to stat for all MD devices I have (raid0, raid1, raid10) - all
> of them reports 0 for time_in_queue field in /sys/block/mdX/stat file.
>
> Is any reason why all raid devices contains no information about time
> spent on requests processing?
>

Wrong mailing list for MD - you want linux-raid@vger.kernel.org

But I can still answer :

These raid levels don't queue requests at all. They just pass them straight
to the relevant underlying devices.

(Now admittedly RAID5 does queue requests but doesn't set the time_in_queue
field, but that is a separate issue).

If you really care about time_in_queue, you need to look at the queues of the
member devices.

NeilBrown
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