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HSG80 and EVA, Windows lun woes behind the scenes

generic_1
Respected Contributor

HSG80 and EVA, Windows lun woes behind the scenes

How from the operating system in the HSG80 and EVA exactly is windows keeping track of which disk is which and to what drive letter the disk maps too? I have been poking through the registry trying to find the disk wwn or something to tie it to a specific disk.

Is a SCSI inquire capable of showing it? If so can someone share a stable exe or C code to compile to show this.

I want to know this so if I yank a lun I know I am pulling the right one for sure :), because if you have many the same size presented its tough to tell.

There has to be a way, or the OS could not do it. Perhaps a HP person could assist on this. Whats the magic?
7 REPLIES
SAKET_5
Honored Contributor

Re: HSG80 and EVA, Windows lun woes behind the scenes

Hi Jeff,

Not sure if this totally helps, but right clicking on a Windows level disk and then looking at the "location" field specifies the controller WWN & the LUN combination for that disk.

My understanding is that these values are what Windows uses to perform persistent identification of Windows level mount points (as in drive letters) and HSG/EVA level Vdisks. I wish Linux had used the same logic - and then LUN persistence under Linux would not have been so much of an issue.

If this does not help and you are after something advanced such as SCU on Tru64 - guess what there is a SCU utility for Windows as well.

Let me know what you think or need more info on SCU and I can provide more info as needed.

Regards,
Saket.
Florian Heigl (new acc)
Honored Contributor

Re: HSG80 and EVA, Windows lun woes behind the scenes

it's not the wwn, but the physical volume id.

I'm quite sure about this - You're using dynamic disks on windows aren't You?

(also, there is something in the registry hive HLKM for the pci\scsi miniport\id\lun collection, but this is dynamic data)

with regular disks and a SCSI or FC JBOD array, switching the disks in their slots will also affect the (DOS int80h,81h,...) drive letter mapping, while with dynamic disks stay as they are supposed to.

thus: use LVM2 :))
yesterday I stood at the edge. Today I'm one step ahead.
generic_1
Respected Contributor

Re: HSG80 and EVA, Windows lun woes behind the scenes

Windows shows the silly dynamic lun number and doesnt show the drive letter its mapped too in its properties. I am trying to figure out a way to yank the info automated but trying to figure out what data I need to be grabbing. I have seen entries for the wwn to lun id on the eva disks. Havent figured that out to a drive letter yet though. I am not seeing them on the EMA. There has to be a way one can tell which lun is which isnt there?

For example two 50 gig luns D1 and D2 on EMA that are the same size is Drive G and H say on windows. How do you know G is D1 or D2 LOL if someone just handed you the box in production with no documentation :). I have talked to windows admins who had their boxes die and go to windows heaven when the wrong lun completely goes away. This should not happen but it does from time to time. There has to be a way to figure this out without guessing.

EVEN ON HPUX for this reason the EVA is a real pain because of this :). Heaven forbid you run out of channels and have to redo em LOL with like sized luns.

Thanks for your replies looking forward to more info on how this stuff works on windows.
generic_1
Respected Contributor

Re: HSG80 and EVA, Windows lun woes behind the scenes

the EMAs are configured as big honkin luns for the most part. EVA has some of both from what I have seen. Is there a way to relate the volume id in dynamic do an actual lun in a EMA and EVA? Especially if you are dealing with disks of like size?
Florian Heigl (new acc)
Honored Contributor

Re: HSG80 and EVA, Windows lun woes behind the scenes

for my defense, let me say I'm almost asleep, but...

WELCOME TO THE WONDERS OF VIRTUALIZATION

(I just couldn't resist that)
yesterday I stood at the edge. Today I'm one step ahead.
generic_1
Respected Contributor

Re: HSG80 and EVA, Windows lun woes behind the scenes

Hasnt anyone in the backline or consulting written utilities do deal with these issues?
generic_1
Respected Contributor

Re: HSG80 and EVA, Windows lun woes behind the scenes

Any HP engineers or folks out there know what kind of data is in the SCSI inq and extend page data for a EMA and eva?

Also it would be nice if someone could explain the field formatting on these devices data because every vendor and device is a bit different how it presents the data.