Re: iSCSI: 2.2.6. Naming & mapping

[Peter Johansson <PJohansson@ACM.org>]

At 04:31 PM 9/14/00, John Hufferd/San Jose/IBM wrote:

>There is NO SUCH THING as an iSCSI LU.

I agree, John, that there is no such thing as an iSCSI LU. But that wasn't 
the issue that was raised.

SCSI targets are addressed by an iSCSI method. If there is more than one 
path by which an iSCSI target is addressable (perhaps a target with more 
than one IP address or URL?), then you had better require unique IDs of 
SCSI LUs. Otherwise it is not possible to discover that what appears to be 
two LUs, reached by different paths, are in fact the same LU.

One may associate a unique identifier with an LU by either a) command set 
methods (SCSI) or b) transport protocol methods (iSCSI in this case).

SBP-2 elected to make an LU's unique identifier visible at the transport 
protocol layer. This was chosen to permit a host to enumerate unique LUs 
(and identify redundant paths) prior to a login to use the device.

I'm not fully conversant with iSCSI device discovery methods, but it might 
be desirable to make a unique LU identifier visible during this stage of 
the process, for reasons analogous to those discovered by SBP-2.




Regards,

Peter Johansson

Congruent Software, Inc.
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Berkeley, CA  94707

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