NonStop NS-Series Operations Guide (H06.12+)

External Devices
External (peripheral), devices, such as tape drives, external disk drives, LAN routers, and SWAN
concentrators, are not backed up by internal batteries. External devices behave differently than
a system during power failure according to the UPS support provided:
Peripheral devices will fail immediately if not supported
by a UPS.
No UPS
A site UPS should support external devices until its
capacity to supply power is exhausted.
With a Site UPS
An optional internal UPS will not support external devices
during power failure.
With an Internal UPS
During a power failure, a ServerNet/DA remains operational during the power-fail delay time,
but the external modular disk and tape subsystems attached to it do not. This type of situation
could result in data-integrity problems if the system software continues processing data from
an external disk drive or tape drive during a short power outage.
If a power failure occurs and the processors resume operations but one or more external devices
fail, data integrity problems can occur. The application programs must be resilient to such device
failures.
ESS Cabinets
ESS cabinets require a site UPS. ESS cabinets are not powered off programatically with a power
failure because they may be attached to other systems.
Air Conditioning
Unless the site UPS provides for maintaining air conditioning, it is possible that the temperature
could rise in the computer room complicating the ability of a system to survive overheating
before shutting itself down. For information about site overheating problems, refer to the NonStop
NS Series Site Preparation Guide.
Preparing for Power Failure
To prepare for power failures, set ride-through time, configure OSM power fail support, and
regularly monitor power supplies and batteries.
Set Ride-Through Time
Ensure that the system is set for the proper ride-through time. The default powerfail delay time
for NS-series systems that are configured with rack-mounted UPSs is 30 seconds. Contact HP
Expert Services for the optimum ride-through time for your system.
The ride-through time is set using the SCF commands to alter the POWERFAIL_DELAY_TIME
parameter. Refer to the SCF Reference Manual for the Kernel Subsystem.
Configure OSM Power Fail Support
You must also configure OSM power fail support by performing a Configure Power Source as
UPS action for at least one processor switch power supply unit (for Integrity NonStop NS16000
series systems) or one IOAM or VIO power supply unit (for Integrity NonStop NS14000, NS1200,
or NS1000 systems). Configuring at least one power supply as being powered by UPS in the
event of a power outage causes OSM to monitor a power outage and, if the AC power is not
restored before the specified ride-through time period expires, OSM initiates an orderly system
shutdown.
152 Power Failures: Preparation and Recovery