[dm-devel] Problems with multipathing

[Christophe Varoqui]

Roger Håkansson a écrit :
>>> but it seems assymmetrical.
>>>       
>
> I guess that you with "asymmetrical" means that paths are only presented
> on one controller at a time, more on that later.
>
>   
Yes, and the "transparent path switching with a penalty" family, which 
your hardware seems to be part of. Those usually don't need a hardware 
handler.

>>> Most hardware in this familly need a hardware
>>> handler, and some need the "queue_if_no_path" feature set too.
>>>
>>> You'll have to find how your array works and try to figure if some
>>> existing hardware handler does the good thing.
>>>       
>
> I've done some testing and it seems that multibus works fine, but when a
> controller fails and the secondary controller takes over, the
> scsi-devices are seen as "dead" and if I, before multipath determines
> both paths to be permanently faulty, do a "echo 1 >
> /sys/class/scsi_device/1:0:0:0/device/rescan", multipath will not fail
> the device.
>
>   
Do failover device nodes get reassigned during the rescan ?
Like, for example, a configured path sda gets removed and a new path sdb 
appears ?
If so, the FC transport class is in charge of the timeout triggering the 
dead devices removal.
A hardware handler wouldn't help here.

Can you paste a before/after scsi rescan "multipath -l" output ?

Regards,
cvaroqui