RE: iSCSI: problem with LUN discovery

["Y P Cheng" <ycheng@advansys.com>]

> From: Nelson Nahum [mailto:nnahum@store-age.com]
> Sent: Wednesday, October 04, 2000 1:54 PM
>
> 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.

Lets make sure we are talking within the same context.  In my view, LUN is
an address, not a name.  It is like the Dept. 514 of IBM Storage Division.
Another company certainly can have a Dept. 514 as well.  If EMC provide data
services to hundreds of companies, the data are housed in different logical
volumes with different LUNs.  The owner of a volume will change, but the
LUNs stay around.  Each LUN or volume consists of many disks, each will have
a GUID so we can tell if someone swap out the disks on us.  One only gets to
see the LUNs assigned to him, aka LUN Masking.  To know which volume a
client is permitted to access has nothing to do with the LUN uniqueness.  A
volume has a unique name like Engineering-of-Connectcom.  But the uniqueness
is only within the EMC Storage Division.  We certain can have a
Engineering-of-Connectcom at IBM Storage Division.  We find the URLs of EMC
and IBM Storage Divisions using a different services.  When login and
authenticate, we get the LUN of Engineering-of-Connectcom. Therefore, I
missed your point on needing WWN for LUN naming.

> 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.

What you suggested should be in the mode page defined by SAM-2.  Given the
access of a particular LUN comes before one has a chance to send the inquiry
command..

Y.P. Cheng, CTO, ConnectCom Solutions Corp.>