To FOM or not to FOM, that is the question!

You have a mutli node P4000 environment, do you need a Fail Over Manager (FOM) or not?

But first, what the hell is a FOM?

The FOM is a specialized version of the SAN/iQ software. It runs as a virtual appliance in VMware that can be run on ESX, ESXi VMware Workstation or VMware player.  It should be installed, preferably on a third site, or at the minimum on another server/esx host/desktop PC completely seperate from the main P4000 environment.

The FOM integrates into a management group as a real manager and is intended only to provide quorum to the cluster, one of its main purposes is to provide quorum in Multi-site clusters.  The FOM does not need to be available for normal day to day operations, it is only used in the event of a quorum dispute between nodes.

Do I need one or not then?

In a two node P4000 cluster, you will need a FOM for automatic failover.  If no FOM is present then if one node loses connectivity, the other node also goes offline as well and you will have to manually failover the LUN’s.   If a FOM is in the same management group as the two nodes, the surviving node will know it is still on the network (as the FOM acts as an arbitrator node) and will stay online.

If you have an odd number of nodes, then you don’t actually need a FOM, as there should never be an even number of nodes available (unless you are really unlucky and have multiple node failures! which isn’t likely).