In this way, the probability of simultaneous resets due to communication failures is minimized. If you're simply power cycling machines with ATX power supplies, you must ensure that the power supply is optioned to power the machine back up when power is restored. IPMI requires a serial connection to each machine being monitored. If your cluster is large enough to require multiple independent switches, then it is desirable for each machine to incorporate delays to minimize the probability of each machine simultaneously shutting down the other one. The most common implementations of remotely controlled power switches support serial or telnet connections.
Serial connections are secure, but can only connect to a single machine.
Telnet connections solve the ability for every machine to connect to the switch. An ideal implementation would use ssh or other advanced authentication mechanisms to access the switch. Unfortunately, at this point, no such switches are commercially available. If a small, inexpensive computer can be dedicated to controlling the switch via serial ports, this could be easily accomplished. It is simple, reliable, and easy to understand method for ensuring data integrity in a shared storage environment.