NonStop NS1200 Planning Guide

NOTE: For NonStop BladeSystems, these actions are located under the Enclosure object. For
NonStop NS-series servers, the actions are located under the Power Supply units located in either
P-switches, IOAM, or VIO modules (depending on system type).
How OSM Power Failure Support Works
NOTE: OSM power failure support works as described only after it has been properly configured.
When OSM detects that one power rail is running on UPS and the other power rail has lost power,
it logs an event indicating the beginning of the configured ride-through time period. OSM
monitors whether AC power returns before the ride-through period ends, and:
• If AC power is restored before the ride-through period ends, the ride-through countdown
terminates and OSM does not take further steps to prepare for an outage.
• If AC power is not restored before the ride-through period ends, OSM broadcasts a
PFAIL_SHOUT message to all processors (the processor running OSM being the last one in
the queue) to shut down the system's ServerNet routers and processors in a fashion designed
to allow disk writes for items that are in transit through controllers and disks to complete.
• Unlike NonStop S-series systems, this system requires a system load after a power failure.
NOTE: Do not turn off the UPS as soon as the NonStop OS is down. The UPS continues to
supply power until that supply is exhausted, and that time needs to be long enough for disk
controllers and disks to complete disk writes.
If a user-supplied rack-mounted UPS or a site UPS is used rather than the HP-supported UPS
models mentioned above, the system is not notified of the power outage. The user is responsible
for detecting power transients and outages and developing the appropriate actions, which might
include a ride-through time based on the capacity of the site UPS and the power demands made
on that UPS.
The R5500 XR UPS and ERMs installed in modular cabinets do not support any devices that are
external to the cabinets. External devices can include tape drives, external disk drives, LAN
routers, and SWAN concentrators. Any external peripheral devices that do not have UPS support
will fail immediately at the onset of a power failure. Plan for UPS support of any external
peripheral devices that must remain operational as system resources. This support can come
from a site UPS or individual units as necessary.
NOTE: OSM does not make dynamic computations based on remaining capacity of the
rack-mounted UPS. The ride-through time is statically configured in SCF for OSM use. For
example, when power comes back before the initiated shutdown, but then fails again shortly
afterward, the UPS has been depleted by some amount and does not last for the ride-through
time until it is fully recharged. OSM does not account for multiple power failures that occur
within the recharge time of the rack-mounted UPS.
This information relates to handling power failures:
• To set ride-through time using SCF, refer to the SCF Reference Manual for the Kernel Subsystem.
• For the TACL SETTIME command, refer to the TACL Reference Manual.
• To set system time programmatically, refer to the Guardian Procedure Calls Reference Manual.
Considerations for Ride-Through Time Configuration
The goal in configuring the ride-through time is to allow the maximum time for power to be
restored while at the same time allowing sufficient time for completion of disk writes for IOs
that passed to the disk controllers before the ServerNet was shut down. Allowing enough time
for sufficient completion of these tasks allows for a relatively clean shutdown from which TMF
recovery is less time-consuming and difficult than if all power failed and disk writes did not
complete. The maximum ride-through time for each system will vary, depending on system
load, configuration, and the UPS capability.
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