Last week I was performing an EMC² VNX5100 FC Block implementation and ran into a “hidden feature”.
The environment was build with 2 VNX5100 storage systems connected to 2 redundant DS-300B FC switches and 5 ESX 4.1 hosts with dual HBA’s connect to both FC switches.
3 FC cables were missing to 3 ESX hosts, so they were temporarily connected with a single FC connection.
Zoning was setup and on Unisphere I configured a storage group containing the ESX hosts and LUN’s.
On vSphere I performed the necessary rescan for storage and configured the VMFS volumes.
The 3 ESX hosts with the single connection of course was showing less paths to the storage.
Then the Fibre cables were delivered and connected.
We modified the zoning to reflect the WWN’s and were expecting that after a rescan on ESX this should have been ok, but in fact the NEW PATHS to the storage were not visible on ESX.
Hmmmm…. what’s going on ??????
I doublechecked the zoning, which was ok and Unisphere was also ok.
Anyway, I went into the “Connectivity Status” and the strange thing was the fact that the 3 hosts were not showing up as part of a storage group at all, while before I already added them and they were already using some LUN’s.
So this was very weird to see.
Then I went into Storage Groups and enabled “Engineering Mode” which will show you some hidden system storage groups like “~filestorage”, “~management” and “~physical”.
I looked into my regular Storage Group for the ESX hosts and the hosts are added.
So then I opened the “~management” Storage Group and noticed that the 3 ESX hosts were ALSO members of this group and I could not remove them.
This is a problem, because of course a host can only be member of 1 Storage Group at the time !!!!
The first thing that came to mind was to remove the ESX host from my regular Storage Group, but this would have been disruptive for the production-ESX hosts, so we had to find another option…
Still in “Engineering Mode”, to overcome the problem, you need to go into your regular Storage Group, open the “Hosts” tab and in “Engineering Mode” you will have an extra button “Advanced“… click “Advanced”
You will then get a list of the hosts and “Used Host Connection Paths”.
I noticed that my 3 hosts were showing the missing paths, but were nog selected.
After I selected the missing paths on the hosts and saved the Storage Group they were automatically removed from the “~management” storage group.
I only had to perform a last Storage Rescan on the VMware Hosts in vCenter and all paths were ok.