Re: iSCSI: problem with LUN discovery

["Nelson Nahum" <nnahum@store-age.com>]

The question is if a storage controller keeps a different GUID for every LUN
created. If not we are in the same problem as WWN, LUN naming.
The question is how to identify a LUN in a storage controller that can
create and delete thousands of LUNs, and that the same WWN, LUN combination
can address different volumes depend on the intiator.
Also to keep this identifier in the EEPROM of the controller is not a good
idea, as cause problems when the controller is replaced.

I think that the best way is to identify a LUN by a string composed by a
<GUID> (or S/N) <date> and <time> of the LUN creation. This method allows to
create infinite LUNs (over the time) in a given controller.
Keeping this string in the media and presented it in a Inquiry page avoids
the identification problems in controllers with multiple channels, that
supports different mapping for multiple initiators.

Nelson Nahum
StoreAge

----- Original Message -----
From: Y P Cheng <ycheng@advansys.com>
To: Nelson Nahum <NNahum@store-age.com>; 'John Muth' <muth@veritas.com>;
<ips@ece.cmu.edu>
Sent: Wednesday, October 04, 2000 9:01 PM
Subject: RE: iSCSI: problem with LUN discovery


> > -----Original Message-----
> > From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
> > Nelson Nahum
> >
> > The problem is that the signature written by the VxVM is not standard
and
> > only is recognized by the Veritas VxVM.
> > Due to the fact that the important thing is to identify the media not
the
> > controller (as Veritas does), the best way is to have the serial number
> > written in the media in a non accessible sector, and loaded by the
> > controller to one of the Inquiry pages of the LU. In this manner no
matter
> > which channel, WWN, LUN  the specific LUN is presented can be
> > recognized by every initiator.
>
> Every 1394 and Fibre Channel node, including disk drives, has a GUID,
Global
> Unique ID. They are saved in EEPROM by manufacturers.  I believe T10 also
> has a mechanism to report a unique name of a device using mode select.
> (Page 83h? Someone help!)  iSCSI should make sure that each device has a
> GUID available by mode select for the initiators.  No need to reinvent
> another mechanism.
>
>
> Y.P. Cheng, CTO, ConnectCom Solutions Corp.