NonStop NS-Series Operations Guide (H06.04+)

Power Failures: Preparation and Recovery
HP Integrity NonStop NS-Series Operations Guide—529869-002
14-3
ESS Cabinets
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 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 40
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.
Monitor Power Supplies
Monitor power-generating equipment and run regular checks on any backup
generators to make sure that you can handle extended power outages.