How to view disk OS unit ID in scsimgr in 11i v3 ?

[John McNulty_2]

Hello,

On EVAs it's possible to set an OS unit ID value on a Vdisk. For a number of years now myself and colleagues have taken advantage of this to easily identify disk LUNs within different EVA racks by using the formula: [rack number] x 1000 + LUN. So for example LUN 3 in rack one would be 1003, and LUN3 in rack two would be 2003.

When used with OS's like Tru64 Unix it makes viewing the DSF + LUN + physical rack association a simple easy command. i.e.

# hwmgr view device | grep IDENT

HWID: Device Name Mfg Model Location
------------------------------------------------------------------------------
212: /dev/disk/dsk1c COMPAQ HSV110 (C)COMPAQ IDENTIFIER=1001
213: /dev/disk/dsk2c COMPAQ HSV110 (C)COMPAQ IDENTIFIER=1002
214: /dev/disk/dsk3c COMPAQ HSV110 (C)COMPAQ IDENTIFIER=1003
343: /dev/disk/dsk4c COMPAQ HSV110 (C)COMPAQ IDENTIFIER=1004
344: /dev/disk/dsk5c COMPAQ HSV110 (C)COMPAQ IDENTIFIER=2001
345: /dev/disk/dsk6c COMPAQ HSV110 (C)COMPAQ IDENTIFIER=2002
346: /dev/disk/dsk7c COMPAQ HSV110 (C)COMPAQ IDENTIFIER=2003
347: /dev/disk/dsk8c COMPAQ HSV110 (C)COMPAQ IDENTIFIER=2004


My question is, how can I view the OS ID information in scsimgr? I've been reading through the docs and man pages and been experimenting a little with scsimgr and haven't found it yet.

Regards,

John

[marie-noelle jeanson]

John,

In scsimgr there are 2 mechanisms, one for dev_id's, one for aliases: maybe one of these will work for you.

For LUNs supporting the SCSI commands SET/REPORT DEVICE IDENTIFIER, you can use the commands 'scsimgr set_devid' and 'scsimgr get_devid'. Need to check if your devices support these SCSI commands. This sets the device ID on the device itself. For instance, to set a value 1001 for dsf disk49:
scsimgr set_devid -D /dev/rdisk/disk49 1001

To retrieve the value:
scsimgr get_devid -D /dev/rdisk/disk49


The other option is to set an alias name for the LUN using the command scsimgr save_attr. But this creates an alias on the HP-UX system only (not on the device itself), and therefore the same alias must be created on all systems. For instance,
To set disk49 alias to 1001
# scsimgr save_attr -D /dev/rdisk/disk49 -a alias=1001

To view aliases of all LUNs as well as the other LUN information
# scsimgr get_attr -D /dev/rdisk/disk49 -a alias


Hope this helps,

Marie.

[John McNulty_2]

Thanks Marie for the response. I'd thought about using those features, and in a scenario where there are only a couple of systems to an EVA it might be useful. The downsides though are:

*) The HP-UX admin has to know which Vdisk WWID numbers presented to the systems belong to which EVA rack. At least initially anyway until she can work out which lunpaths lead to which EVA and can use that knowledge to map them to other disks. Often the sys admin is not the same person as the SAN admin.

*) It's a bit long winded as it has to be repeated individually for every system connected to the SAN. Just picking up the OS Unit ID from the EVA involves no extra work as assigning the OS Unit ID is a simple inclusive step when creating a Vdisk.

*) Post install changes to the SAN will not automatically be reflected on the system until the sysadmin deliberately detects and makes a change. So on going accuracy depends on a human driven process (the weakest link in the chain).


I've read the scsimgr.pdf downloadable guide from docs.hp.com front to back, and had a good play with a v3 system here connected to an EVA and come to the conclusion this can't be done. It's a shame, as it seems you can get at just about every other interesting aspect of a disk with scsimgr. I wonder why this was overlooked. Perhaps the development engineers are used to working with XPs with the OS Unit ID is mandated and is not an optional value.

If anyone from HP is reading this and knows who to forward this to, could you please submit this as an enhancement request for a future version.

Thanks again. John

[John McNulty_2]

Hi Marie. FYI, I tried:

# scsimgr set_devid -D /dev/rdisk/disk9 1001

The Vdisk is on an EVA 4000 running VCS 6.1. A subsequent get_devid on that device returned a "?", so that option doesn't work at the moment.

Setting the alias worked as that's only updating the local database.

John

[marie-noelle jeanson]

John,

I understand, thanks for providing this feedback to HP. The only thing you can do at the moment is verify if a later firmware supports the SET/REPORT DEVICE IDENTIFIER SCSI commands.

Marie.

[Santosh Rao]

John,

Did you try :

#scsimgr get_devid all_lun

As Marie-Noelle explained earlier, the scsimgr set_devid can be used to set the DEVICE IDENTIFIER and scsimgr get_devid can be used to get the device identifier.

Rgds,
Santosh