[dm-devel] different LUN numbers under the same dm device

[Hannes Reinecke]

On 06/06/2012 09:27 PM, Brian Bunker wrote:
> Our company produces a multiple port Fibre Channel storage array. We are continually plagued
> by this problem. We get a dm device which combines paths for
different LUN's. We would like
> to understand why this is happening. Wouldn't this problem almost
certainly lead to a data
> corruption?
> 
Most likely; given that the two LUNs indeed refer to different disks.

> Thanks,
> Brian
> 
> 3624a93700a14254d729923840001000b dm-11 PURE,FlashArray
> size=500G features='0' hwhandler='0' wp=rw
> `-+- policy='round-robin 0' prio=1 status=active
>   |- 1:0:0:12 sde  8:64   failed faulty running
>   |- 0:0:0:12 sdd  8:48   failed faulty running
>   |- 0:0:0:10 sdar 66:176 active ready  running
>   `- 1:0:0:10 sdba 67:64  active ready  running
> 
> Of the 4 paths to dm-11, we can see two paths are for LUN 10 and the other two are for LUN 12.
> We have 24 other dm devices which have only the expected 2 paths.
> 
Check the output of 'sg_vpd -p di /dev/sd(e|d|ar|ba)'.

'sde' and 'sdd' should be identical (well, the bits for 'Addressed
logical unit' should be), as should 'sdar' and 'sdab'.
'sde' and 'sdar', on the other hand, should _not_.

Given the above, however, I strongly suspect they are.
Looks like your LUN WWID generation code is buggered.

But I guess you can always blame Nic Bellinger :-)

Greetings to Joern Engel.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare at suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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