A power controller for data centers.

One of the major features of an SNMP-enabled device is that it can spontaneously inform the SNMP manager of important events or alerts. When SNM P connectivity is enhanced with additional software features, the result can be a unit with power control and communication capabilities that exceed

In a general IT environment, SNMP is valuable as a tool for efficient large-scale management of devices, as it provides a consistent communication-and-control protocol. At present, two versions of SNMP are generally supported, with SNMPv2 providing additional protocol enhancements. For the most flexibility, the power distribution unit (PDU) should support both SNMP v1 and v2.

For example, an SNMP can allow read/ write capability, plus "trap" commands, by which the PDU can asynchronously inform the network-management station of a significant event. This is a useful function for devices that control the power to critical sub systems. E-mail notification of alerts is a part of the above protocol and both of these series can be configured to send these warnings to up to two e-mail addresses.

Besides providing these alerts, the units can also send a log via e-mail showing user activity. SNMP therefore provides a cost effective method of improving system alarm monitoring by moving from dedicated lines and into the LAN-based environment.

While SNMP lacks any authentication capabilities, which creates a vulnerability to a variety of security threats, the more robust features of some PDUs incorporate HTTP 1.1 (64 bit encrypted) digest authentication. This level of security adds user name/password verification and allows the administrator to disable any unused interfaces, thereby minimizing possible intrusions. Networking setup should allow dynamic host configuration protocol or any public/private address.

A full-featured PDU will allow for the setup of an administrator login level, plus the login of multiple users. In this implementation, the administrator will have access to all of the possible control and reporting functions, and users can be limited to control of specific outlets, a condition that provides isolation of the controlled subsystems.

In this configurable environment, outlets may even be grouped together so that a single command can control multiple subsystems. This is especially useful to control systems utilizing N+I power supplies, where power to all power supplies must be removed simultaneously.

To provide the most robust of operating environments, the PDU software should be highly configurable, which would include the ability to set outlet names, unit names, network settings, sequence times and reboot times. The inclusion of an internal systems clock will allow the administrator to schedule time and date-dependant on/off control events.

Interconnection for remote access is primarily accomplished by an Ethernet 10/100 protocol and RJ-45 port. To maximize adaptability and configurability, the PDU should have a serial RS-232 connection capability, and a telnet interface will also add to the connectivity value. For enhanced functionality, the PDU should include FTP capability to allow simple and easy upgrades to the unit's firmware.

A PDU should also feature effective EMI/RFI filtering, incorporating both common mode (line to ground) and differential mode (line to line) interference reduction. Spike and surge protection is also an essential feature; the EN55024 1998 standard forms the specification basis for these features.

Electrical requirements suggest that the PDU should be rated for at least a 20 amps input current, and while 120 VAC rating would be standard, system flexibility would be enhanced if a unit with a 85-264 VAC rating is available. Additionally, quality and reliability concerns suggest that the PDU be ISO 9001:2000 registered.

Remote-control capability using SNMP integrated into a PDU can significantly enhance the alert-reporting and system-control capabilities, and selecting such a unit with integrated intelligence capability will generally provide an overall cost savings. A full-featured unit will provide a variety of interface options and multiplatform compatibility.

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This article was provided by Roger Edelson, senior technical writer for Pulizzi Engineering, Santa Ana, Calif.