Subject: Re: Some questions about naming (newbie)

From: "Justin R. Bendich" <[email-masked]>
Date: Wed, 18 Apr 2001 11:20:04 -0500

> 3. A LUN WWN is at the SCSI LUN level, and can be used for identifying
>    LUNs regardless of whether the underlying transport is FC, parallel
>    SCSI, or iSCSI.  However, most FC devices do not support the LUN
>    WWN, and use serial numbers, device IDs, and other mechanisms to
>    correlate them.  To do this, one must implement device-type-specific
>    code.

> Anyway, those were just a few observations that might help.
Thank you -- they do.

> On question 3, keep in mind that an INQUIRY is done at the SCSI
> level, and is independent of the SCSI transport mechanism used.
> Therefore, the VPD information would not return anything that would
> reflect an iSCSI identifier.  The ability to return a LUN WWN (from
> (3) above) on this page really is a SCSI-level thing, and has nothing
> to do with FC other than that it shares the same address format.
I think i understand your point:
A device might not be iSCSI only -- it might also have FC, plain SCSI
(what's the official name for that?) interfaces, so the device doesn't
necessarily know its node-name; that's the interface's responsibility?
I don't actually need a node-name -- any identifying string will do.
But the node-name is nice because the iSCSI naming spec requires it
(along with the actual LUN number) to uniquely identify the LUN.
That's something i don't know to be available through any other specifi-
cation. Am i right there?

> At any rate, in order to connect to a SCSI device via iSCSI to do
> the INQUIRY, you must first log in to the target at the iSCSI level.
> To do this, you would already have the iSCSI name (formerly WWUI),
> so you should already have the information you need without the
> inquiry data.
Yes, but in order for my (application-level) code to do that, it has to be
aware that the transport is iSCSI, and many OSs take great pains to hide
that information from application-level code. MS even tries to make ATA
hard disks look like SCSI (gag).
So it would be nice if:

1. Table 111 of the SCSI Primary Command set (T10 995d Rev. 11a)
   included an additional identifier type "iSCSI node-name"
2. Devices supporting iSCSI were strongly recommended (even though
   this can't be required for the reasons discussed above) to report this
   identifier on VPD page 0x83.

> Mark A. Bakke
> Cisco Systems
> [email-masked]
> 763.398.1054

Justin