Each SAN Volume Controller node monitors the operational state of the uninterruptible power supply to which it is attached.
If the 2145 UPS-1U reports a loss of input power, the SAN Volume Controller node stops all I/O operations and dumps the contents of its dynamic random access memory (DRAM) to the internal disk drive. When input power to the 2145 UPS-1U is restored, the SAN Volume Controller node restarts and restores the original contents of the DRAM from the data saved on the disk drive.
A SAN Volume Controller node is not fully operational until the 2145 UPS-1U battery state indicates that it has sufficient charge to power the SAN Volume Controller node long enough to save all of its memory to the disk drive. In the event of a power loss, the 2145 UPS-1U has sufficient capacity for the SAN Volume Controller to save all its memory to disk at least twice. For a fully charged 2145 UPS-1U, even after battery charge has been used to power the SAN Volume Controller node while it saves dynamic random access memory (DRAM) data, sufficient battery charge remains so that the SAN Volume Controller node can become fully operational as soon as input power is restored.