ESXi Fibre Channel Configuration Maximums

Today we ran into a issue where we could not see all the LUNs presented to our hosts. In this case, we had multiple Nimble arrays connected already. We added 6 more LUNs from one of the Nimbles to our initiator group that is going to the ESXi host. We checked the logged in initiators, the initiator group, and the zones and EVERYTHING appeared to be connected correctly. We have 4 initiators coming out of the ESXi host and all 4 were logging into the fabric, array, and showing connections to the LUNs.  However… not all of the LUNs were showing up under storage adapters on the host.  This is what we saw:

HBA1 sees 0, 1, 2 and 3

HBA2 sees 0, 1 and 2

HBA3 sees 0, 1, 2, 3, 4 and 5

HBA4 sees 0, 1 and 2

Needless to say… That was kind of odd since everything was showing up as logged in. We rescanned multiple times and we restarted the vSphere Client for good measure.  Eventually, we ran the command:  esxcli storage core adapter rescan –all from the command line.  When we did THAT… the system spit out a bunch of errors that were pretty close to this:

The maximum number of supported paths of 1024 has been reached. Path vmhba2:C0:T0:L3 could not be added.
The number of paths allocated has reached the maximum: 1024. Path: vmhba5:C0:T6:L28 will not be allocated. This warning won’t be repeated until some paths are removed.

 If you look here:

 http://www.vmware.com/pdf/vsphere5/r55/vsphere-55-configuration-maximums.pdf

You will see that ESXs supports a MAXIMUM of 1024 paths per SERVER.  This is not a per ADAPTER thing…

We’ve seen some of the ESX Maximums in the past with iSCSI but usually we hit the device limit long before we hit the path limit.  

So two things to learn from this:

  • Be aware that the vSphere Client won’t always be verbose about what’s going on.
  • Be aware of the ESXi Configuration Maximums. The way they have it is that whichever limit you hit first wins. It’s not a this, this, and this sorta thing.  It’s a this or this or this kind of thing.

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