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LUN ID limitation?
https://3parug.com/viewtopic.php?f=18&t=2853		 Page 1 of 1
Author:  KKW [ Thu Apr 12, 2018 2:55 am ]
Post subject:  LUN ID limitation?
hi @ all,

when i want to export a volume to a windows server (2012 R2) is there a limitation about the LUN IDs ?

I export a vol with lun id 5 no problem. if i want export the same vol to the same server and i export the vol with lun id 301 i can not see the vol on the server

thanks
kkw
Author:  ailean [ Thu Apr 12, 2018 4:18 am ]
Post subject:  Re: LUN ID limitation?
Most things support LUN ids in the 0-255 range I think, beyond that often requires tweaking HBA, driver, OS, array settings.
I've not had to go beyond 200 on most boxes, 3PAR think supports much higher if required but I'd check you're HBA BIOS settings to see if there's a scan beyond 255 option. Have also seen on older kit a need to see at least one LUN in a low range (maybe below 16) before it'll scan any higher.
Extended scanning will probably increase boot times too.
Author:  markinnz [ Thu Apr 12, 2018 4:44 am ]
Post subject:  Re: LUN ID limitation?
KKW wrote:
hi @ all,

I export a vol with lun id 5 no problem. if i want export the same vol to the same server and i export the vol with lun id 301 i can not see the vol on the server



If you are presenting the same LUN to the host twice with different LUN IDs I would think the multipathing software would just treat the extra LUN as different paths to a volume it already knows about ... I've used that trick with other OSs not tried Windows though :-)

Plus as Ailean says .. lots of OSs stop counting after 255.
Author:  KKW [ Thu Apr 12, 2018 8:54 am ]
Post subject:  Re: LUN ID limitation?
Thanks for the feedback and the explanation. I understood the topic.
Author:  Richard Siemers [ Thu Apr 12, 2018 9:41 pm ]
Post subject:  Re: LUN ID limitation?
As previously mentioned, LUN# 301 is too high, keep it under 254.
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