Re: fc transport creates second set of targets for devices in an "md"

Michael Reed
2006-06-09T16:26:40Z

James Smart wrote:
> The data that would be most interesting is a recursive listing of the
> device via the /sys/devices tree. This would show the host, rports,
> targets, and sdevs. Getting a copy of this both before, when missing,
> and after they are reconnected. The additional contents to look at
> is : contents of /sys/class/fc_remote_ports.

I'll capture data and post later today.

>
> Also - it's unlikely that FC is to blame here. The above data would
> show whether we had the same WWN's, reused target id's or not, and
> what the midlayer reassigned to h/c/t/l's. It would show if the FC
> transport is in error or not.

Agree. Sometimes the title is used to draw attention to a problem. ;)
It worked.

>
> Relative to volume managers - yes, they have some difficulty. However,
> the tact they plan on taking is to bind the device based on the udev
> name that get built on it. Which means - md would have issues, but DM
> is planning for it.

So, do any volume managers work correctly now? By "correct" I mean,
when the device returns, will they be able to access it?

>
> I do have a request to make an option for the transport to not remove
> the devices upon disconnect.

I understand why. If this does what I suspect it will, please add SGI
to the list. We should probably discuss requirements.

Mike

>
> -- james
>
> Michael Reed wrote:
>> I created an md device on two fibre channel disks, sde and sdf.
>> I then disabled the switch port to which the hba is connected.
>> After the remote port time out messages, I re-enabled the switch
>> port. Three things happen that are weird. First, two unexpected
>> responses while scanning. Second, the creation of sdm and
>> sdn. Third, the md device remains inaccessible.
>>
>> I don't think this is working the way it's intended to. I
>> suspect it will cause big problems for multi-path volume managers
>> in a fail back situation.
>>
>> Mike
>>
>