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Chapter 3. Replacing controller unit components 35
Battery
The battery CRU contains rechargeable batteries and a battery-charger board. The battery
CRU plugs into the front of the controller unit (see
Figure 19 on page 37 ) where it
provides backup power to the controllers cache memory. During a power outage, a
properly charged battery CRU maintains electrical current to the controllers for up to five
days with 256 MB cache memory installed and up to 3 days with 512 MB cache memory
installed. Therefore, all data stored in memory is preserved as long as the batteries can
sustain power to the cache memory. However, the battery does not provide power to the
rest of the system during a power outage. Therefore, the system is not able to write data to
drives without a backup power source.
Servicing notes
Consider the following when servicing the battery in the controller unit:
• The battery has a three-year life expectancy. Replace the battery every three years or
whenever it fails to hold a charge. Using the controller unit in a hot environment
(above 35
º
C or 95
º
F) lowers the life expectancy of the battery. Under these conditions,
you might need to replace the battery more often.
• The service label on the battery provides a blank line for recording the last date on
which the battery was serviced (see
Figure 18 on page 36 ). Check this label to
determine when to replace the battery. For information about using the software to
track battery age, refer to the Netfinity FAStT Storage Manager documentation and
online help.
• If a battery fails, the fault light on the battery glows. For more information about
indicator lights, see
"Checking the indicator lights" on page 15 .
• If you replace the battery and still experience battery problems (for example, loss of
battery power to the controllers or batteries not charging properly), the controller unit
might have defective components or connections. Check the storage-management
software for indications of other component failures.
Replacing a failed battery
When instructed by the storage-management software, replace the battery.
Attention: Because the battery CRU is a sealed unit, you must replace the entire CRU
(not just the batteries) in order to keep the battery backup system in working
order. Opening the battery CRU voids your warranty.
1 Use the storage-management software to check that there is no data in cache and that
all caching has stopped. Data in cache is unprotected if a power outage occurs while
the battery CRU is out of operation.