Re: [PATCH] scsi: Allow 64-bit LUNs during report lun scan

[Hannes Reinecke <hare@suse.de>]

On 02/14/2013 11:44 PM, Jeremy Linton wrote:
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> On 2/14/2013 4:04 PM, Elliott, Robert (Server Storage) wrote:
>> Like James notes, LUNs should generally be treated as opaque values.
>
> 	Maybe another issue to consider is how they are being displayed in userland.
> A device with two luns using one of the alternative lun addressing methods is
> going to get some pretty strange looking lun numbers showing up in userspace
> if they aren't decoded properly.
>
No. LUNs with anything other than peripheral addressing do look 
weird even nowadays.
Cf IBM DS8000 presents me with LUNs like:

# lsscsi
[0:0:0:49409]wlun    IBM      2107900          .107  -
[0:0:0:1085358099]disk    IBM      2107900          .107  /dev/sda

where the second maps to LUN 401340b100000000.

Again, the initiator _must not_ attempt to decode the LUN.
To stick with the above example, LUN 400040b100000000 and LUN
40b1000000000000 do refer to the same LUN number, albeit on a 
different Level. And it's totally up to the target which physical 
LUN these numbers refer to. The initiator has to map these numbers 
to different devices; to figure out whether the devices are 
identical one would have to look at VPD page 0x83.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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