So you just moved all your servers into that fancy new data center with redundant everything, including redundant UPSs.

Your servers have redundant power supplies and with separate 30amp feeds from the two UPSs,  you carefully plug one power supply into one of the two feeds and the other power supply into the other feed.  Great, you are now protected if/when one of the UPSs goes offline.

But what about your switches and firewalls and those few remaining legacy servers, all of which have only one power supply? How can you get the benefits of the data center’s redundant UPSs and separate power feeds when you have devices with only one power cord?

Easy!  You just need a PDU (Power Distribution Unit) that plugs in to two separate power feeds, uses one feed as the primary, the other as secondary, and automatically fails over and back between the two.  Recall that we are not a reseller for any hardware or software, but we have been using the Tripp-Lite PDUMH20AT device in our own rack space now with good success.  This unit has 20amp plugs and receptacles; there is also a 15amp model.  The 20amp model costs about $360.

For really remote data center management, there is an optional SNMP card you can use to manage each of the power receptacles, program sequenced power up, etc.

Attentive engineers will note that this device introduces a new single point of failure, which is true.  Our experience however has been that data centers with redundant UPSs will, perhaps every two years or so, cycle offline the UPSs for major maintenance. Using a device like this enables your gear to stay up during UPS maintenance (or a single UPS failure).

One way to overcome this PDU’s new single point of failure, for example in the case of a pair of failover firewalls, would be to plug one of the firewalls into this device and the other firewall into one of the standard PDUs already in the rack.

Everything comes with tradeoffs, but our view is that a PDU with an automatic transfer switch represents a terrific way to provide devices with single power supplies in a data center rack the benefits from fully redundant power feeds.

If you have any questions regarding your data center configuration, please give us a call at (207) 772-5678.

This entry was posted on Tuesday, July 28th, 2009 at 8:30 AM and is filed under Networks. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.