[dm-devel] Why all raid devices do have zero 'time in queue' value?

NeilBrown neilb at suse.de
Sun Mar 11 02:10:51 UTC 2012

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

> 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 at 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.

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