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Troubleshooting a vSCSI Mapping

April 17, 2018

I was recently asked to help troubleshoot a vSCSI mapping. My colleague was running an SAP HANA POC workload on POWER, and is new to the platform. At the time an older version of HMC code was being used, so we still had access to the classic HMC interface. Since mapping the virtual adapters and managing the profiles is a manual process, there's always the potential for errors. And unfortunately, mistakes were made with the adapter numbering.

As an aside, in the enhanced version of the HMC GUI, all of this is automated. The enhanced version may still be unfamiliar to many, but it does provide this among other benefits. Regardless, we're going to have to make the transition, because IBM has made it known that the classic interface is going away and support for x86 hardware appliances is being phased out.

In any case, even though we verified that the adapters were set up correctly in the profiles and the LUN was mapped to the correct adapter, a Linux OS that had been previously installed on the LUN couldn't be booted. It didn't appear as a as a bootable device. At this point, the question was posed: "are you sure the LUN is mapped correctly? Can the LPAR really see it?"
 
As I often do, I decided to try an internet search, and came across this thread. It's from 2013 but it's precisely what I was hoping to find:

In the first reply:

During SMS processing "LIST ALL DEVICES" will ONLY show devices that SMS thinks are BOOTABLE.

Then further in the thread:

You can try and boot the partition in openboot. Then type ioinfo and pick vscsi, this should show you your LUNs.

In our case it was as simple as booting the LPAR normally (i.e., not into SMS mode) and then selecting option 8, the open firmware prompt. From there we could select the proper disk and get a confirmation that it did indeed see the LUN, along with the LUN's size.

This was enough to convince us that our mappings were fine. We then used bootable media to make the LUN bootable.

Although many of us use NPIV or shared storage pools these days, mentally file this anecdote away in the event you ever find yourself using vSCSI.

Posted April 17, 2018 | Permalink

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