HP StorageWorks 2000 Series Reference Manual page 62

Shut down a controller module before you remove it from an enclosure, or before
you power off its enclosure for maintenance, repair, or a move. Shutting down a
controller module halts I/O to that module, ensures that any data in the write cache
is written to disk, and initiates failover to the partner controller, if it is active.
If you shut down both controller modules, you lose access to SMU, CLI,
and FTP and users lose access to data. To restart the controllers, turn off both
power-and-cooling modules and then turn them back on.
To shut down a controller:
1. Select Manage > Restart System > Shut Down/Restart.
2. In the Shut Down panel, select a controller option.
3. Click Shut Down.
A warning might appear that data access redundancy will be lost until the selected
controller is restarted. This is an informational message that requires no action.
4. Confirm the operation by clicking OK.
If an iSCSI storage system is connected to a Microsoft Windows host, the
following event is recorded in the Windows event log: Initiator failed to connect to
the target.