The DDP officially supports UPSs from APC. During a power cut, the DDP can be remain powered on until the UPS runs out of battery and perform a soft shutdown, hence keeping the DDP hardware and data safe.
In order to further configure your APC UPS, you can login to the DDP by ssh and edit the following file:
/etc/apcupsd/apcupsd.conf
You can then edit the configuration fields as per you needs.
Most commonly, the fields you'll want to modify will be:
BATTERYLEVEL 5
If during a power failure, the remaining battery percentage (as reported by the UPS) is below or equal to to the specified value, a system shutdown will be initiated.
MINUTES 3
If during a power failure, the remaining runtime in minutes (as calculated internally by the UPS) is below or equal to the specified value, a system shutdown will be initiated.
TIMEOUT 0
If during a power failure, the UPS has run on batteries for the specified amount of seconds or longer, a system shutdown will be initiated. A value of 0 disables this timer.
Once you modified the configuration file, you can test your settings by running the following command, which will guide you through the possible scenarios:
apctest
You can also check the UPS current status at any time by running the following command:
apcaccess