NonStop NS2400 Series Planning Guide

NonStop System With Rack-Mounted UPS and Data Center UPS in Parallel
Figure 61 shows an example of a non-supported configuration in a NonStop system with the left
PDUs connected to the rack-mounted UPS, and the right PDUs connected to the data center UPS.
In this configuration, OSM manages and monitors the rack-mounted UPS. However, OSM does
not manage or monitor the data center UPS.
Figure 61 NonStop System With Rack-Mounted UPS and Data Center UPS in Parallel
When the utility power fails, OSM detects a UPS AC Input not Present event from the
rack-mounted UPS. OSM does not recognize the data center UPS. OSM does not detect that the
data center UPS is running on battery and the UPS battery runtime. OSM does not initiate the
controlled shutdown of the I/O operations and processors.
• The rack-mounted UPS shuts down before the data center UPS.
• If the utility power is not restored before the data center UPS shuts down, any data in the
NonStop system disk drive write cache that has not been transferred to the disk drive media
is lost.
To prevent data loss during a utility power failure, you must manually disable the Write Cache
Enable (WCE) option on all the disk drive volumes. For information on how to disable the WCE,
see the SCF Reference Manual for the Storage Subsystem (G06.28+, H06.05+, J06.03+).
• When the utility power is restored, you can enable the WCE.
• During the utility power failure, the system can continue to run until the data center UPS runs
out of power or until it shuts down.
Non-Supported UPS Configurations 197