HP-UX 11.31 on rx8640 with HBAs has strange naming for symmetrix LUNs

[Ravi-Joshi]

Hello,

We are seeing weird behaviour with HP-UX 11.31 for symmetrix LUNS naming convention.  We have rx8640 and all 4 cells

are into one npar (npar 0). It runs HP-UX 11.31 and PowerPath. There are 4 HBAs which connect to SAN switches to array.

We presented a LUN to it. This LUN is used by another production hp-ux server running 11.31. The issue is with

naming convention on this rx8640.

I ran ioscan -m dsf and it shows me

/dev/rdisk/disk48        /dev/rdsk/c18t12d4
                         /dev/rdsk/c20t2d2
                         /dev/rdsk/c19t2d2
                         /dev/rdsk/c17t12d4

If you look at legacy devices (ctd), the target and disk (that is t and d numbers) have to be same no matter what path you

take from the server to the DMX lun. But here it shows  c18t12d4, c17t12d4 same but c20t1d2, c19t2d2 different.

That is each pair have same t and d number but not all. I would expect all t and d number to remain same. The c number

will change which is correct.

On 11.23 and 11.11,  this never happened. I am wondering does 11.31 creates ctd devices in a different way.

Has anbody seen this issue in field on a server running hp-ux 11.31 that has more than 2 HBAs.

Thanks for your response.

RJ

[Patrick Wallek]

I have seen servers that have different d numbers for the same LUN.  In one case one path was something like c4t1d2 and the other path was c5t1d3.

I do not have a good explanation.

[Ravi-Joshi · Accepted solution]

Sorry to post the solution late. I had to call EMC and look at the ctd devices. They found the solution. The t and d

numbers come from the way fibre cables are connected to the FA port on the switch. It is good to follow

industry best practices to connect the switches. Sometimes, strange configurations are created.

So it is possible to have t and d different for the same LUN, if the FA port mapping is different for the LUN.