Ups Battery - Sun Microsystems StorEdge T3 Installation, Operation And Service Manual

5.2.3

UPS Battery

The UPS battery is located within the power and cooling unit. The battery provides
backup in case of a complete AC power failure and will sustain power to the disk
tray long enough to flush cache data to the drives.
During a power failure, if the battery is flushing cache data to the drives, battery
power becomes depleted. Once AC power is available, the battery will recharge.
While the battery is recharging, write-behind cache mode is disabled and write-
through cache mode is enabled until the battery is fully recharged. The battery
recharge could take up to 12 hours, depending on the length of the power outage
and the amount of cache data that was flushed to the drives.
5.2.3.1 Battery Maintenance
The Sun StorEdge T3 disk tray has been factory configured to initiate a battery
refresh cycle that occurs automatically once every 14 days. This battery refresh cycle
involves a discharge of the battery followed by a recharge. The refresh cycle is
sequential; the second power and cooling unit will not start a refresh until the first
power and cooling unit successfully completes the refresh cycle, ensuring that only
one battery in a disk tray is refreshed at a time. This refresh cycle verifies the health
of the battery. During the refresh, if a problem is detected with the battery, future
refresh operations are suspended until the problem is fixed. If this happens, write-
behind caching is turned off automatically as a safety precaution. A refresh cycle
will not begin unless both power and cooling units are in optimal condition.
Note – During the discharge period of a refresh cycle (approximately 12 minutes),
write-behind cache is turned off.
A battery refresh operation in progress is indicated in the syslog file. During the
battery refresh operation, the battery health is determined by the discharge time of
the battery. This time is written into the syslog file and is displayed as battery hold
time. If the discharge time of the battery is greater than six minutes, the battery is
considered healthy. If the battery is not healthy, the system will disable the battery,
disable write cache, and indicate that the power and cooling unit needs to be
replaced. The following is an example of the battery hold time as displayed in the
syslog file:
May 21 00:19:22 driver24 BATD[1]: N: u1pcu1: hold time was 1159 seconds.
You can use the refresh -s command to view an active refresh operation. Refer to
the Sun StorEdge T3 Disk Tray Administrator's Guide for more information on this
command.
5-10 Sun StorEdge T3 Disk Tray Installation, Operation, and Service Manual • July 2000