AIX Migration and multipathing : how ?

[stephnane1]

Hello.

I'm doing a migration of a nim server from AIX 6.1.7 to 7.1 . This server is a LPAR behind 2 VIO Servers.
For this operation, I put iso of DVD on the VIO then I created a virtual optical disc.
My server has only one "San Volume" (hdisk0 in 6.1.7 version) - 3Par storage, seeing by 8 paths.

When I boot on the ISO, the install is stuck with this message :

0516-1775 varyonvg: Physical volumes hdisk0 and hdisk1 have identical PVIDs (00c
7de65c233b82c).                                                                 
0516-780 importvg: Unable to import volume group from hdisk7.                   
Could not import the root volume group.                                         
   ID#        OPTION                                                            
     1        Continue                                                          
     2        Perform System Maintenance and Then Continue                      
   Enter ID number:

If I enter in Maintenance Mode, all hdisks have the same PVID (due to multipathing).
Is there is simple way to work around this ? Can I load a multipathing driver before this phase ? Can I start the migration in another way ?

How can I temporary disable paths of this LPAR on VIO servers ?

Thank you

 

[DukeSSD]

Same way you installed it..

If your storage is not recognised by AIX as MPIO capable then on the storage limit the lun masking / paths to 1.

You'll get away with more for a normal boot if the drivers or kernel extensions support it but you'll need storage support or SAN support to get involved if ever you need to maintenance boot for recovery, and this just adds more time to your recovery!

As your NIM server is essential in a DR situation you need to get this sorted out right away.

Also there is really no point in 8 paths to a lun, 2 is usually enough - especially for a vscsi VIO client, 4 is usually as many as are ever required even for a npiv or a dual fibre card LPAR, more is usually just pointless.

You don't say if the NIM server is accessing the storage via npiv or vscsi, I guess npiv from the sheer number of paths, but local storage is the best way to go for both a NIM server and its underlying VIO servers rootvgs when you REALLY need them!

HTH

 

[stephnane1]

Yes, we are in npiv.
The NIM server only use disks through npiv access.

 

[AIXLogician]

Stephnane1,
If you have 8 paths, that means those are connections and not each physical disk, if you are saying you are seeing those disks then probably you are using EMC MPIO (powerpath), each disk seen is a path, you should be really concern about something like hdiskpowerX (which I assume will be hdiskpower0).
You might be seeing those eight paths because of their connection on Storage Array.
Say you are giving two connection from each VIO so total paths for each disk is 4, but each fibre cable might in turn is connected to two adapters on storage (1 is going to fabric and two from fabric to SAN array).

Now coming to your point of migration of OS on NIM.
Try to dynamically move the CV/DVD rom from VIO to NIM.

SARFARAZ AHMED SYED,
Sr. Systems Engineer