Adding new hosts to vSphere cluster with RDM disks

33I was working with a customer to assist them in upgrading their cluster from 5.1 to 6.o u2.  They had started off with a 2 host cluster, then added a third node to the cluster.  The SAN is an HP EVA6000.  When VMware was first set up and volumes were provisioned and presented, there were only the first two hosts in the cluster.  After the third host was added, naturally the SAN admin presented the volumes to the new host.  What was missed was making sure the LUN number for each volume that was previously presented to just the first two hosts was the same LUN number when presented to the third host.

 

We were running into some problems performing a vMotion of a VM with RDM’s to the new host.  It was complaining that the target host couldn’t see the disks, even though I was able to verify both in the GUI and CLI that it absolutely could see it.  I was able to vMotion between the two original hosts however so this had me stumped.  I had the SAN admin double check the presentation for the RDM disk on that VM and that’s when I saw the LUN number mismatch.

 

The fix was to power off the host, unpresent the volumes, present the volumes making sure to use the same LUN number as the other two, then power the host back up.  After doing this, our problems were solved!

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