HP LeftHand P4000 Virtual SAN Appliance Software - Manual (Page 127)

Disaster recovery using a virtual manager
The virtual manager functions as an on-demand manager in a disaster-recovery situation. As an
on-demand manager, it can be used to regain quorum and maintain access to data.
Management group across two sites with shared data
Using a virtual manager allows one site to continue operating if the other site fails. The virtual
manager provides the ability to regain quorum in the operating site if one site becomes unavailable,
or in one selected site if communication between the sites is lost. Such capability is necessary if
volumes in the management group reside on storage systems in both locations.
Management group in a single location with two storage systems
If you create a management group with only two storage systems and do not have a Failover
Manager, a virtual manager will be automatically added to the management group. The addition
of the virtual manager provides the capability of regaining quorum if one manager becomes
unavailable.
Storage system maintenance using a virtual manager
A virtual manager can also be used during maintenance to prevent loss of quorum. Adding a
virtual manager to a management group enables you to start the virtual manager when you need
to take a storage system offline for maintenance.
Requirements for using a virtual manager
It is critical to use a virtual manager correctly. A virtual manager is added to the management
group, but not started on a storage system until the management group experiences a failure and
a loss of quorum. To regain quorum, you start the virtual manager on a storage system that is
operating and in the site that is operational or primary.
Table 36 Requirements for using a virtual manager
What it means Requirement
Total number of
managers, including the
virtual manager Number of regular
managers running Disaster recovery scenario Use a virtual manager with an even
number of regular managers running
on storage systems
5 4 Two separate sites with
shared data
3 2 Two storage systems in
management group
You cannot add a virtual manager after quorum has been lost. The virtual
manager must be added to the management group before any failure occurs. Add a virtual manager when creating
management group.
The virtual manager should run only until the site is restored and data is
resynchronized, or until communication is restored and data is resynchronized. A virtual manager must run only until
the site is restored or communication
is restored.
Correct uses of a virtual manager are shown in Figure 52 (page 128) .
Virtual manager 127