VMWARE Virtual SAN networking

VSAN networking can be a bit tricky to troubleshoot. Before I go deeper into the topic here is a very important concept to remember about VSAN clusters.

Given any VSAN cluster remember the following:

** “Introduction to Virtual SAN Networking

Before getting into network in detail, it is important to understand the roles that nodes/hosts can play in Virtual SAN. There are three roles in Virtual SAN: master, agent and backup. There is one master that is responsible for getting CMMDS (clustering service) updates from all nodes, and distributing these updates to agents. Roles are applied during cluster discovery, when all nodes participating in Virtual SAN elect a master. A vSphere administrator has no control over roles.”

** from Cormac’s troubleshooting guide

That is a lot to digest but if break it down you can see some key principles about a VSAN cluster to remember.

The roles in VSAN:
A master
B agent
C backup.

There is one master.
If you see more than one master there is something not quite right with you VSAN CLUSTER.

The VSAN admin does not control which node will be the master.

Example:
Log into each node of a three node VSAN. The normal pre-req for troubleshooting make sure ssh is enabled.

Run the following command on each node:
~ # esxcli vsan cluster get

Cluster Information will output below.
NODE 1

Cluster Information
Enabled: true

Current Local Time: 2015-03-30T22:38:38Z
Local Node UUID: 55197cee-f530-4966-5ea6-a0369f58b8e4
Local Node State: MASTER
Local Node Health State: HEALTHY
Sub-Cluster Master UUID: 55197cee-f530-4966-5ea6-a0369f58b8e4
Sub-Cluster Backup UUID:
Sub-Cluster UUID: 551374b5-03f9-7bd6-6257-a0369f58b8e8
Sub-Cluster Membership Entry Revision: 0
Sub-Cluster Member UUIDs: 55197cee-f530-4966-5ea6-a0369f58b8e4
Sub-Cluster Membership UUID: a5ce1955-f5e5-5663-d338-a0369f58b8e4

Node 2
~ # esxcli vsan cluster get
Cluster Information
Enabled: true
Current Local Time: 2015-03-30T22:38:38Z
Local Node UUID: 55197cee-f530-4966-5ea6-a0369f58b8e4
Local Node State: MASTER
Local Node Health State: HEALTHY
Sub-Cluster Master UUID: 55197cee-f530-4966-5ea6-a0369f58b8e4
Sub-Cluster Backup UUID:
Sub-Cluster UUID: 551374b5-03f9-7bd6-6257-a0369f58b8e8
Sub-Cluster Membership Entry Revision: 0
Sub-Cluster Member UUIDs: 55197cee-f530-4966-5ea6-a0369f58b8e4
Sub-Cluster Membership UUID: a5ce1955-f5e5-5663-d338-a0369f58b8e4

Node 3
~ # esxcli vsan cluster get
Cluster Information
Enabled: true
Current Local Time: 2015-03-30T22:56:46Z
Local Node UUID: 54f9dc6f-8674-f412-364d-a0369f58b5a8
Local Node State: BACKUP
Local Node Health State: HEALTHY
Sub-Cluster Master UUID: 551374b5-03f9-7bd6-6257-a0369f58b8e8
Sub-Cluster Backup UUID: 54f9dc6f-8674-f412-364d-a0369f58b5a8
Sub-Cluster UUID: 551374b5-03f9-7bd6-6257-a0369f58b8e8
Sub-Cluster Membership Entry Revision: 1
Sub-Cluster Member UUIDs: 551374b5-03f9-7bd6-6257-a0369f58b8e8, 54f9dc6f-8674-f412-364d-a0369f58b5a8
Sub-Cluster Membership UUID: d6da1955-e2f8-38eb-d7f0-a0369f58b8e8

See the image below for the error seen in the web client.

From the output above can you see the problem?

IMG_2285.PNG

IMG_2285-0.PNG

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