Setting Up The DAU 2-17
Turning Off AC power
1. Power off the host system.
The host writes cache data to the disk array unit.
2. Confirm that the cache data from the host is successfully written into the
disk array unit. To do this, check the DISK ACCESS LEDs located on the
rear panel of each controller. If the DISK ACCESS LEDs are flashing, data
remains in cache memory of disk array unit. Writing cache data onto disk
could take as long as 5 minutes. See Figure 1-10, J3 for the location of the
DISK ACCESS LED.
3. Turn off the AC power to the DAU. A power switch is located on the rear
panel of each power supply. See Figure 1-9.
!
CAUTION
When the DAU power is turned off before the cache data is
written to disk, the BACKUP LED on the controller is lit and
the disk array unit enters the backup mode. If the backup
mode lasts for more than three days (in the full-charged
condition), the cache data may be lost. Therefore, if the
BACKUP LED is lit, immediately turn on the disk array unit.
Since the data write is an automatic process, check the data
is completely written to the disk and then turn off the power.
4. Turn off AC power to the disk enclosure (if installed).
!
CAUTION
Turn off the power of host system, disk array unit, and disk
enclosure in that order. Turning off the power of disk
enclosure first may lose the data.
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