User guide

Power On/Off procedures 5–7
Hitachi Unified Storage VM Block Module Hardware User Guide
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.
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.
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 HUS VM for
two weeks or more, ask technical support to move the batteries to a storage
system that is being used, or turn the storage system on to standby mode
for at least 3 hours once every two weeks.
If you store the system for more than two weeks and do not disconnect the
cache destage batteries, when you restart the system, the batteries will
need to charge for at least 90 minutes before the cache will be protected.
To prevent the batteries from discharging during long term storage, call
technical support and ask them to disconnect the battery jumpers on the
cache boards.
3 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.
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.
Item Description Item Description
Note: The storage system generates a SIM when the cache destage
batteries are not connected.
Note: The storage system generates a SIM when the cache destage
batteries are not charged to at least 50%. The LEDs on the front panel of
the cache boards also show the status of the batteries.