atacontrol rebuild and iostat

[Cy Schubert]

(Silly me, my first attempt didn't cc the list, sorry.)

In message <04cf01c3ea3f$56394960$0464a8c0 at spotripoli.local>, "Putinas 
Piliponis" writes:
> Hmm, another notice...
> I created array, right now it's rebuilding
> 
> atacontrol status ar0
> ar0: ATA RAID1 subdisks: ad4 ad6 status: REBUILDING 3% completed
> 
> to check is it really doing what I expect I run
> iostat ad4 ad6 1
> and I see 0 transfer to devices:
> pilkis at freebsd:/usr/src# iostat ad4 ad6 1
>       tty             ad4              ad6             cpu
>  tin tout  KB/t tps  MB/s   KB/t tps  MB/s  us ni sy in id
>    1 1219  0.50   0  0.00   0.50   0  0.00  17  0  6  1 76
>    0  180  0.00   0  0.00   0.00   0  0.00   0  0  2  3 96
>    0   60  0.00   0  0.00   0.00   0  0.00   0  0  2  2 97
>    0   60  0.00   0  0.00   0.00   0  0.00   0  0  2  2 95
>    0   60  0.00   0  0.00   0.00   0  0.00   0  0  0  0 99
>    0   60  0.00   0  0.00   0.00   0  0.00   1  0  1  2 96
> 
> to be sure what I didn't miss something I also run
> iostat ar0
> also no transfers 0.00MB/s
> 
> Why nothing ?

Iostat doesn't see the I/Os because RAID rebuilds occur within the 
controller, the I/Os are not initiated in the O/S nor any of its utilities, 
therefore the FreeBSDS kernel doesn't see them. The O/S doesn't see the 
I/Os. Atacontrol see 3% because it specifically queries the controller for 
that information.

This is true of all hardware RAID controllers and true of all operating 
systems.


Cheers,
--
Cy Schubert <Cy.Schubert at komquats.com>        http://www.komquats.com/
BC Government                     .                       FreeBSD UNIX
Cy.Schubert at osg.gov.bc.ca         .                     cy at FreeBSD.org
http://www.gov.bc.ca/             .            http://www.FreeBSD.org/