Cache Destage Batteries; Battery Life - Hitachi HUS VM Hardware User's Manual

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Cache destage batteries

The environmentally friendly nickel hydride cache destage batteries are used
to save storage system 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 storage system 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, an authorized support person connects the batteries.
Note: The storage system generates a SIM when the cache destage batteries
are not connected.

Battery life

The batteries have a lifespan of two years, and will hold a charge for that
time when disconnected. 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.
Hitachi Unified Storage VM Block Module Hardware User Guide
Figure 5-2 Battery backup operations
Description
Power failure occurs
The cache memory data and the
storage system configuration are
backed up to the cache flash
memory on the main boards. The
backup continues even if power is
restored during the backup.
Power On/Off procedures
Item Description
2 The storage system continues to
operate for 20 milliseconds and
detects the power failure.
4 Unrestricted data backup. Data is
continuously backed up to the
cache flash memory. The cache
flash memory consists of two 80
GB SSDs, one on each of the two
boards in each main blade.
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