The options for all the Dell UPSs are USB (default, cable included), RS232 (not default, no cable included) & Network Management Card (optional H910P card).

The USB option is very good for SMB type applications where the UPS is just shutting down a few servers. The USB connection method relies on the Dell UPS Management Software to broadcast the UPS status across the LAN to other servers being protected by the UPS. In the event of “low battery” the server connected to the UPS by USB broadcasts the status message to client servers to call the shut down process.

Of course this relies on the host server being available in order to broadcast the message. To eliminate this reliance on the host server, the user can use the H910P network management card (NMC) which allows an unlimited number of servers to communicate directly with the UPS over the LAN. It uses SNMP as it’s main communication protocol. The NMC also allows users to log into the UPS through a web browser to monitor and control the device, and also to alarm to SNMP management tools such as DMC, OpenView, Tivoli etc. The NMC can also send email alerts to users by generating an email through the client’s email server without the need to have the Dell UPS software installed. Note that for a server to shut down, it still needs to have the Dell UPS software installed as this is the program which calls the shutdown procedure.

The NMC is also a requirement if the customer is using an ESXi 4.0 system as the USB or RS232 will not work with it (VMWare issue, not Dell UPS issue). There have been improvements in ESX 4.1 which may mean USB can work but this is not yet verified.