topic Re: Fix for 8 lun limit in Operating System - HP-UX

Fix for 8 lun limit

Paul Wewel — Thu, 17 Aug 2000 17:34:44 GMT

I heard there is a patch out to extend the 8 lun limit in 11.0. Anyone know about it?

Re: Fix for 8 lun limit

Marcel Eken_2 — Fri, 18 Aug 2000 05:40:32 GMT

Hi Paul,

There is not a patch for ux 11.x to increase the numbers of lun's. I think that if you can't get more then 8 lun's it is probably a limitation of the devices attached to the scsibus.

For example an autoraid 12 or a Nike FC/30 supports only 8 lun's.

Marcel,

Re: Fix for 8 lun limit

Patrick Wessel — Fri, 18 Aug 2000 06:10:54 GMT

Marcel,
It's a limitation from the OS, not from the array. There are only 7 Bit for the value of the LUN.

Paul,
I'm not aware that there is a patch to change that Limitation.

Re: Fix for 8 lun limit

Stefan Stechemesser — Fri, 18 Aug 2000 06:25:25 GMT

SCSI-2 only uses 3 bits for adressing the LUN - that's the reason why only 8 LUNs can be accessed. SCSI-3 will theoretically allow 2^64 LUNS, but currently HPUX 11.0 still can only handle 8 LUNS ...

Re: Fix for 8 lun limit

Patrick Wessel — Fri, 18 Aug 2000 07:05:48 GMT

my fault, of cause it's just 3 bit...

Re: Fix for 8 lun limit

Paul Wewel — Mon, 21 Aug 2000 13:34:20 GMT

I heard there was something called "volume set addressing", that was originally only enabled for certain devices that HP supported. It basically only used 8 LUN's but enumerated the path number for each additional 8 LUN's. I heard it was generally released for all devices in 11.11. I was looking for some details on how you take advantage of this.

Re: Fix for 8 lun limit

Andy Monks — Mon, 21 Aug 2000 13:50:44 GMT

There is an enhancement request to increase the limit, currently being considered by the lab. I don't know the status however.

Re: Fix for 8 lun limit

Patrick Wessel — Tue, 22 Aug 2000 13:55:42 GMT

For more information about VSA check the "FC60 Advanced User's Guide" page 217-220
You find the manual at this location: http://www.hp.com/essd/download/fc60_adv.pdf

Re: Fix for 8 lun limit

Paul Wewel — Tue, 22 Aug 2000 18:32:47 GMT

Great info. Thanks. So is VSA in 11.11 open to anybody or is it still restricted to HP "approved disks" meaning they sell it disk arrays?

Re: Fix for 8 lun limit

Dave Wherry — Tue, 22 Aug 2000 18:50:46 GMT

Paul,
Are you thinking of Fibre Channel? There you can have multiple targets on the same controller:
c2t4d0 - c2t4d7 &
c2t5d0 - c2t5d0 and so on. I think the limit is 128 LUNs on a channel.

Re: Fix for 8 lun limit

Paul Wewel — Tue, 22 Aug 2000 20:42:39 GMT

Yes, fibre channel arrays. Most of them will support up to 32 lun's under a target but in order for the HP-UX systems to have access to all these volumes they must implement the volume set addressing method to get above 8 per target. This is described well in the FC60 document referenced earlier in this thread but what I have been told is you have to be one of HP's array types in order for them to allow this extended addressing. I also heard that in 11i they may have made this open to all disk arrays. How would one obtain HP-UX 11.11 (11i) upgrade? Is it out on the web or do I need to order it through HP? Does anyone know if this is open now and whether there is a spec available that describes how you need to present yourself in Inquiry and Report Lun's commands to take advantage of it?

Re: Fix for 8 lun limit

Dave Wherry — Wed, 23 Aug 2000 19:22:16 GMT

Paul,
I've actually not heard of volume set addressing. I may be using it and not realize it.
I've used EMC Symmetrix, HP XP256 arrays and FC30 arrays. They would all be considered one of HP's array types. On both UX 10.20 and 11.0 on these array types I have not had more than 8 LUNs per target. However, I have had multiple targets per card giving me many more than 8 LUNs on the EMC and XP. With the performance of the FC30 I do not want that many LUNs. I want to get off of it.
I inherited the 10.20 systems and as is typical they were Highly Patched (HP). The 11.0 systems I built and added the XP256 to them. As with any HP product there was a list of patches to install. I can't tell you if any of them specifically addressed the set addressing method. One or more might have.
As for 11.i, I saw in the HP World magazine that it will be released this fall. No date set.
When you ask "how you need to present yourself in Inquiry and Report Lun's commands", again I can't tell you anything specific. The inq command for EMC and the xpinfo command for the XP256 have always worked with reporting these LUNs. Nothing special to do.