Cache Destage Batteries; Battery Life - HP HPE XP P9500 Manual

prevent slow data throughout 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 16 Battery backup operations
Item

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, Hewlett Packard Enterprise
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.
When the batteries are connected and the power is off, the batteries slowly discharge. They will
have a charge of less than 50% after two weeks without power. When fully discharged, the
batteries must be connected to power for three hours to fully recharge.
48 Power On/Off procedures
Description
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.