Testing Device Failure

[Dan Track]

On Wed, Oct 14, 2009 at 10:20 AM, Bryn M. Reeves <bmr at redhat.com> wrote:
> On Tue, 2009-10-13 at 22:12 +0100, Dan Track wrote:
>> On Tue, Oct 13, 2009 at 5:22 PM, Dan Track <dan.track at gmail.com> wrote:
>> > Hi,
>> >
>> > I've got two SAS links to my San, I want to test failure/recovery by
>> > eleminating and device node. The easiest way is to manually unplug a
>> > controller link and see what happens. I'd like to know how I can do it
>> > via Linux, and then re-enable the device node? I have two device nodes
>> > /dev/sda and /dev/sdb.
>> >
>> > Thanks
>> > Dan
>> >
>>
>> Hi
>>
>> Does anyone have any thoughts on this.
>>
>> Thanks
>> Dan
>>
>
> If you're using device-mapper to combine the two paths into a single
> multipath device you should see a change in the output of the multipath
> -l/-ll commands when you unplug the cable (and if the unplugged path was
> the path that was previously carrying I/O there'll also be a change of
> path groups and I/O should begin flowing over the second path).
>
> As long as you have multipathd running the failed path should be
> re-added to the multipath map when it returns and depending on the
> failback settings in use will trigger another path group switch.
>
> Regards,
> Bryn.
>
>
Thanks for that Bryn. I'll do just that.