HP advised me to have 4 regular managers (1 on each node) and a Failover Manager (FOM) configured for quorum consistency in a management group that has two clusters, with two nodes for each cluster.
For example, let's say you need to update the firmware on Node 3 in Cluster 2. If you have Node 4 running a regular manager, and a FOM in place, you can bring Node 3 down without loosing any quorum consistency. When Node 3 comes back online, it will take approximately 15 minutes for it to re-sync its data with the cluster.
Another alternative is to use a "Virtual Manager". From HP:
A Virtual Manager is added to a management group, as shown in Figure 52 on page 151, but is not
started on a storage system until a failure in the system causes a loss of quorum. Unlike the Failover
Manager, which is always running, the Virtual Manager must be started manually on a storage system
after quorum is lost. It is designed to be used in two-system or two-site system configurations which
are at risk for a loss of quorum
As a small side note, you do not want to use a FOM and a Virtual Manager together, its either one or the other.....
If you have an HP Passport, you can go to this link to download a ESX, Hyper-V, or standalone version of the FOM:
Scroll to the bottom of the page, click "Receive for free" and sign in with your HP Passport.
HP StorageWorks P4000 SAN Solution user guide