Linux Archive

Linux Archive (http://www.linux-archive.org/)
-   Device-mapper Development (http://www.linux-archive.org/device-mapper-development/)
-   -   Why all raid devices do have zero 'time in queue' value? (http://www.linux-archive.org/device-mapper-development/643058-why-all-raid-devices-do-have-zero-time-queue-value.html)

George Shuklin 03-10-2012 09:33 PM

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.

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel

NeilBrown 03-11-2012 01:10 AM

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
--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel


All times are GMT. The time now is 10:51 AM.

VBulletin, Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO ©2007, Crawlability, Inc.