The Big Decision: Smart vs. Switched Data Center PDUs

Recently, many customers have inquired about whether they should implement smart or switched power distribution units (PDUs) into their data centers. After all, when looking at the two products side by side, they appear to be almost identical, as both products offer the following features:

• Branch circuit protection
• Input current monitoring
• Environmental monitoring
• Access, security and communications
• An expansion module
• Interoperability with Server Technology’s Sentry Power Manager (SPM)

There is one major difference, though, between smart and switched PDU: A switched PDU provides the ability to toggle power on and off on a per-outlet basis. As such, a switched PDU typically offers more control and flexibility on an outlet where it’s being used.

Conversely, a smart PDU will provide the same level of critical power and environmental data, but will not allow you to make changes to the outlet from a central location. Smart PDUs are more for monitoring and reporting purposes.

Here are some reasons a business would consider investing in a switched PDU:

Rebooting and power-up sequencing: When a core network device fails, it doesn’t always need to be taken in for service, or manually inspected. Sometimes, all it takes is a reboot to correct the underlying error. Reboots aren’t always easy, though, particularly for multisite data centers or colocation facilities. They can be time consuming and expensive, if they require sending technicians out to the actual data center to complete the task. Using a switched PDU, reboots can be performed remotely from a Web interface—thus potentially eliminating the need to deploy service technicians.

Switched PDUs also come in handy following power outages. In this case, operators need to be careful to avoid power surges when powering up equipment, as this can lead to additional network downtime. A switched PDU can enable staged power-up sequencing, allowing the network to ease back up to scale. 

“Locking out” unused outlets: Resources like space, power and cooling come at a premium price in medium-to-large data centers—especially in growing facilities. For this reason, it can be very challenging trying to deploy new IT equipment safely. Before a device can be installed into a cabinet, it’s vital to track the cabinet’s power usage and environmental conditions over time. Otherwise, installing the device could prove to be dangerous.

Suffice to say, in a medium-to-large environment it can be very difficult trying to keep a running historical account of each cabinet’s usage history and available capacity. With the help of a switched PDU, though, managers can easily identify outlets which are not safe for use based on aggregated historical data. Then, the outlet can be toggled off so that no equipment can be added to it. 

Scheduling power loads: Many data centers waste power by continuing to run equipment during off-hours when the network is not being fully used, usually because it is more cost-effective to keep the equipment running and saves time over having to manually reboot. A switched PDU allows operators to strategically schedule each outlet to avoid wasting power. As we explained in this white paper, one government agency was actually able to reduce power usage in their POC data center by an average of 50 percent for any given week using a switched PDU. It should also be noted that switched PDUs are ideal for identifying and eliminating “zombie” servers, or comatose servers that use large volumes of data over time by running idly.

The aforementioned points are just some of the benefits to using a switched PDU, and the white paper contains many more.

Keep in mind, though, that determining the right type of PDU can be very complex. And in some cases, a switched PDU may not be the best choice to fit your needs. For example, if you are managing a single facility, there may be little need to use remote management technologies; your staff members may prefer to perform outlet changes manually. The scope of your operation, your risk factor for downtime, your budgetary allowance and your staff members’ preferences should all be considered when deciding what type of PDU to use.