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it-rex

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AIX LUN major minor vs serial#

we have a RAC system with LUNS attacjed to both nodes we have created ASM aliases using major and mainor number..

ASM1 till ASM 10 are correctly showing the major minor numbers in both nodes...
and everything is running fine..
and this is best practice by IBM and ORACLE.

but we have a new Jr SA who is saying this is wrong as although major and minor are the same for each LUN on both Nodes the Lun Serila number is different.

we know that the configuartion is correct.
but how LUN serial could be different and major minor are identical?
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it-rex

ASKER

Although 2 disks on 2 nodes are using the same major and minor number

Will it be possible that output of lscfg will show 2 different serial numbers.
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ASKER

So what would explain having 2 LUNS shared between 2 lpars
With same major and minor
But lscfg shows different lun names
??????
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ASKER

both
hdisk8@node1
and
hdisk4@node2

they have the major and minor numbers

ls -la hdisk8
brw-rw----    1 grid     asmadmin     18, 14 Jan 17 09:02 hdisk8

ls -la hdisk4
brw-rw----    1 grid     asmadmin     18, 14 Jan 17 09:11 hdisk4


@node1

lscfg -vpl hdisk8
  hdisk8           U9179.MHD.10854A0-V42-C42-T1-W500507680140B9D7-L32000000000000  MPIO FC 2145

        Manufacturer................IBM    
        Machine Type and Model......2145            
        ROS Level and ID............0000
        Device Specific.(Z0)........0000063268181002
        Device Specific.(Z1)........020060c
        Serial Number...............60050768018305CFC000000000000B8C


@node2

lscfg -vpl hdisk4
  hdisk4           U9179.MHD.10854A0-V44-C44-T1-W500507680140B9D7-L22000000000000  MPIO FC 2145

        Manufacturer................IBM    
        Machine Type and Model......2145            
        ROS Level and ID............0000
        Device Specific.(Z0)........0000063268181002
        Device Specific.(Z1)........020060c
        Serial Number...............60050768018305CFC000000000000B7C

As you have mentioned the I think I see both
The WWN and the LUN are the same.
but what is the line that says

Serial Number means and what it signifies?
It seems that these nodes are running as LPARS with dedicated HBAs (or NPIV) on the same hardware (Power 780).

Anyway, the LUN number is not the same! hdisk8 has LUN 32 and hdisk4 has LUN 22.

The serial number is composed of parts of the WWN and some more information. This number is unique, and is also different, as you said.

So I'm rather sure that these are different disks!

The major/minor numbers aren't of any significance across nodes, they're only used internally. Up to now I wasn't aware that you could create an ASM diskgroup using major/minor! Or do you mean the "/dev/hdiskx" entry instead?

There is a really unique disk identifier at a higher level in AIX, which is the PVID. This identifier is written on the disk and cannot change.

Run

lspv

on the nodes and search for hdisk4 and hdisk8, respectively. If the displayed IDs (second column) are different you can be really sure that these disks are not the same!
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ASKER

With ASM on AIX we can not have PVID it is a requirement for pvid to be null
OK,

but the disks come from the same storage server (SVC) and have different LUNs, so they are different disks.

Moreover, thay have different serial numbers.

You can check these numbers on the SVC by means of the "lshostvdiskmap" command.

Here, too, you will see that it's two different disks.
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ASKER

thanks all