Re: FC SAN UDID

John E. Malmberg wrote:

Mark Iline wrote:

Does anyone know if it is possible to access a Fibre Channel SAN disk's UDID via a SCSI sense mode or set mode command under OpenVMS ?


It is not a mode to be set or sensed.

HSG, HSV, and MSA Devices use a Digital Private SCSI commands to read / write the UDID.

The MSA and HSV will also allow the SCSI Report Device Identifier command to read the UDID. In these cases the value of 0 indicates no identifier set.

There are corresponding commands to set the UDID. I do not know if they are supported or implemented in the HSG or HSV.

The XP array does not appear to allow the UDID to be set through SCSI commands as the UDID is calculated based on other parameters.

Third party devices may or may not allow a UDID to be set.

The Alpha consoles only support using the Digital Private SCSI command to obtain a UDID. Integrity systems will support both.

Recent OpenVMS versions will first try the official SCSI command and then the Digital private command as a fallback.

Thanks. I think I had several misconceptions (and there may be several more where they came from...)

Am I right in thinking that the UDID is returned in "inquiry page 83h" ?

That being the case, if a storage controller returns a page with an appropriate UDID for each LUN in response to the official SCSI command, that would be enough for recent versions of OpenVMS to configure and use those devices ? [How recent a version ? 7.3-2 ?]

It's useful to know that the Alpha consoles only use the Digital private command. That means there's no point in trying to use wwidmgr as a test of whether a valid UDID is available. It would also make it more awkward, but not impossible, to boot.

Someone in the VMS storage group may be able to give you that information. Or if you have access to the source listings, you can see what OpenVMS does.

I can not give exact information as all my stuff is in a moving van at an unknown location.

Shame. *If* I'm right on the above, it would be really useful to know the way that the UDID is laid out in page 83h.


Mark
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Relevant Pages

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