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Do I need a LUN 0 defined

Keith C. Patterson
Frequent Advisor

Do I need a LUN 0 defined

I was under the impression that a LUN 0 was required on all HP HBA's in order to see any LUNS afterwards.
Is this incorrect? If so are there patches that allow you not to have to define a LUN 0.
Also, how does this apply to sequential LUN numbering? I know there are patches that get around this.
Thanks.
12 REPLIES
David Bell_1
Honored Contributor

Re: Do I need a LUN 0 defined

Keith,

If you are referring to the VA7100, you are correct, LUN 0 must be defined. It can be as small as 10MB. However, all hosts must have WC permission to this LUN in order to communicate with the array. To my knowledge, there are no patches to ignore this requirement.

Sequential LUN number patches are for instance, you have LUN 1,2,3 and 10,11,12. Without the sequential LUN patches, you would only see LUN 1,2,3 and 10,11,12 would not appear. This does not mean you have to have LUN 1,2,3, you could have LUN 1,10,20,30, etc. However, you must still have LUN 0 for array communication.

HTH,

Dave
harry d brown jr
Honored Contributor

Re: Do I need a LUN 0 defined

Keith,

What kind of disk sub-systems are we talking about?

live free or die
harry
Live Free or Die
Keith C. Patterson
Frequent Advisor

Re: Do I need a LUN 0 defined

Hitachi 9900.
Howver, isn't this a limitation of the HBA driver anyway. As a result the array type wouldn't matter.
Am I correct?
Thanks.
harry d brown jr
Honored Contributor

Re: Do I need a LUN 0 defined


It's the device that needs a LUN 0. I have servers on a SAN without a LUN 0 to an HBA.

live free or die
harry
Live Free or Die
Keith C. Patterson
Frequent Advisor

Re: Do I need a LUN 0 defined

Did you require any specific patches for this?
Kurt Beyers.
Honored Contributor

Re: Do I need a LUN 0 defined

Keith,

The LUN 0 is required if Windows systems are connected to the SAN as well. If you only have
HP-UX systems connected to the SAN, LUN 0 is not required.

Kurt
Keith C. Patterson
Frequent Advisor

Re: Do I need a LUN 0 defined

This getting rather confusing.
I actually caontacted HP support and had a storage engineer contact me.
He informed me that a LUN 0 is ALWAYS required.
From my testing I have never been able to see anything unless I have a LUN 0 defined.
I appreciate all the feedback but I think there is some bad info. going around.
Thanks.
harry d brown jr
Honored Contributor

Re: Do I need a LUN 0 defined

Keith,

I think I'm very wrong:

http://bizforums.itrc.hp.com/cm/QuestionAnswer/0,,0x766050011d20d6118ff40090279cd0f9,00.html

We need Insu Kim to pipe in here :-)

live free or die
harry
Live Free or Die
Duncan Edmonstone
Honored Contributor

Re: Do I need a LUN 0 defined

Wasn't this all sorted out by a patch? - see the following link:

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0xa66142308663d611abdb0090277a778c,00.html

HTH

Duncan

HTH

Duncan
David Bell_1
Honored Contributor

Re: Do I need a LUN 0 defined

Keith,

To avoid confusion on my post, I'm specifically referring to the VA7x00. The information in my previous post for that device is correct. As to the Hitachi, I've not worked with that device and cannot speak to it's configuration.

Good Luck,

Dave
Keith C. Patterson
Frequent Advisor

Re: Do I need a LUN 0 defined

Well everyone,
Here's output from an ioscan when I attach to a Hitachi 9200 array:
See attachment.
If you notice, I don't have a LUN 0 on target 0 but am able to see subsequent LUNS. I do, however, have a LUN 0 on target 1. It appears that you do need a LUN 0, but not necessarily on the same target.
William Shaw
Frequent Advisor

Re: Do I need a LUN 0 defined

Regarding your last message about LUN 0 appearing on target 1 (but no LUN 0 on target 0), at the HDS array you will see that that device is actually LUN 8, but the HP OS maps any LUN greater than 8 to the next target, wrapping around to LUN 0 again. A LUN 16, for instance, would therefore map to target 2, LUN 0. So you don't *really* have any LUN 0 out there, it's just how HP maps LUNs higher than 0 through 7.

Regards, Bill