Installation Manual

20 Using the power management features
Server power-on with iLO 4
Nonblade servers
Before the introduction of ProLiant Gen8 servers, some ProLiant servers (ML and DL) could be
powered on through the power button within a few seconds after AC power was connected. If
an AC power loss occurs on ProLiant Gen8 or Gen9 servers with iLO 4, approximately 30 seconds
must elapse before the servers can power on again. If the power button is pressed during that
time, it will blink, indicating a pending request.
This delay is a result of the iLO firmware loading, authenticating, and booting. iLO processes
pending power-button requests when initialization is complete. If the server does not lose power,
there is no delay. A 30-second delay occurs only during an iLO reset. The power button is disabled
until iLO is ready to manage power.
A power-button watchdog allows the user to power on the system using the power button when
iLO does not boot successfully.
The iLO firmware monitors and configures power thresholds to support managed-power systems
(for example, using Hewlett Packard Enterprise power capping technology). Multiple system
brownout, blackout, and thermal overloads might result when systems are allowed to boot before
iLO can manage power. The managed-power state is lost because of AC power loss, so iLO
must first boot to a restore state and allow power-on.
c-Class blade servers and Synergy compute modules
With ProLiant Gen8 and Gen9 blade servers and Synergy compute modules, the server cannot
power on until the system is identified, iLO determines the power requirements of the server and
enclosure or frame, and verifies that power is available. When AC power is applied to a server
in an enclosure or frame, there is a short delay. If the system does not power on when the button
is pressed check the OA (c-Class) or HPE OneView (ProLiant or Synergy) for more information.
If an issue prevents server power on, an event is reported in the IML.
Brownout recovery
A brownout condition occurs when power to a running server is lost momentarily. Depending on
the duration of the brownout and the server hardware configuration, a brownout might interrupt
the operating system, but does not interrupt the iLO firmware.
iLO detects and recovers from power brownouts. If iLO detects that a brownout has occurred,
server power is restored after the power-on delay unless Auto-Power On is set to Always
Remain Off. After the brownout recovery, iLO firmware records a Brown-out recovery event
in the iLO Event Log.
Graceful shutdown
The ability of the iLO processor to perform a graceful shutdown requires cooperation from the
operating system. To perform a graceful shutdown, the iLO health driver must be loaded. iLO
communicates with the health driver and uses the appropriate operating system method of
shutting down the system safely to ensure that data integrity is preserved.
If the health driver is not loaded, the iLO processor attempts to use the operating system to
perform a graceful shutdown through the power button. iLO emulates a physical power-button
press (iLO momentary press) to prompt the operating system to shut down gracefully. The
behavior of the operating system depends on its configuration and settings for a power-button
press.
For more information about the iLO drivers, see “iLO drivers and utilities” (page 32).
Server power-on with iLO 4 245