Cache Destage Batteries; Battery Life; Long Term Array Storage - HP XP P9500 Owner's Manual

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 20 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, HP Technical Support representative connects the batteries.
NOTE:

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.
NOTE:
least 50%. The LEDs on the front panel of the cache boards also show the status of the batteries.

Long term array storage

While connected, the cache destage batteries will completely discharge in two to three weeks
without power applied. If you do not use a P9500 for two weeks or more, contact HP Technical
68 Power On/Off procedures
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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.
The disk array generates a SIM when the cache destage batteries are not connected.
The disk array generates a SIM when the cache destage batteries are not charged to at
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