HP XP7 Owner Guide (H6F56-96006)

Battery backup operations
The XP7 is designed so that it cannot lose data or configuration information if the power fails. The
battery system is designed to provide enough power to completely destage all data in the cache
if two consecutive power failures occur and the batteries are fully charged. If the batteries do not
contain enough charge to provide sufficient time to destage the cache when a power failure occurs,
the cache operates in write through mode. This synchronously writes to HDDs to prevent slow data
throughput in the cache. When the battery charge is 50% or more, the cache write protect mode
operates normally.
When a power failure occurs and continues for 20 milliseconds or less, the disk array continues
normal operation. If the power failure exceeds 20 milliseconds, the disk array uses power from
the batteries to back up the cache memory data and disk array configuration data to the cache
flash memory on each cache board. This continues for up to ten minutes. The flash memory does
not require power to retain the data. The following illustration shows the timing in the event of a
power failure.
Figure 25 Battery backup operations
DescriptionItem
Power failure occurs
The storage system continues to operate for 20 milliseconds and detects the power failure.
The cache memory data and the storage system configuration are backed up to the cache flash memory
on the cache boards. The backup continues even if power is restored during the backup.
Unrestricted data backup. Data is continuously backed up to the cache flash memory.
Cache destage batteries
The environmentally friendly nickel hydride cache destage batteries are used to save disk array
configuration and data in the cache in the event of a power failure. The batteries are located on
the cache memory boards and are fully charged at the distribution center where the disk array is
assembled and tested. Before the system is shipped to a customer site, the batteries are disconnected
by a jumper on the cache board. This prevents them from discharging during shipping and storage
until the system is installed. At that time, HP Technical Support representative connects the batteries.
NOTE: The disk array generates a SIM when the cache destage batteries are not connected.
Battery life
The batteries have a lifespan of three years, and will hold the charge when connected. When the
batteries are connected and power is on, they are charged continuously. This occurs during both
normal system operation and while the system is in standby mode.
72 Power On/Off procedures