Load Shedding – How to Cap Power Consumption

Scott Fier
September 13, 2017

Would you like to put a hard power capacity limit on a rack to ensure failover success or put a limit on a set of racks?

Load shedding can be the answer to preventing rack circuit-failover failure.

When dealing with PDUs there are already limits to the load capacity of a single device. It comes in the form of floor PDU circuit breakers. However, the capacity limit of a rack can exceed the limit of a single rack circuit. This is due to the fact that you typically load balance between two or more circuits. In other words, each circuit could be under capacity but when you add the loads together (loss of one circuit/failover) you exceed the capacity of one of those circuits. Under these circumstances, you could lose the whole rack because a failover would not succeed.

One way to make sure you don't exceed the capacity of a single rack or any set of racks is to utilize these key features of the Raritan PX line of PDUs:

1.  Load Shedding — You pre-configure a group of outlets on a PDU that you want to be turned off when a particular event arises.  The load shed outlet group may just be unused outlets and the load shed just keeps these outlets from being used.

2.  LUA Scripting — Create a LUA script with JSON-RPC that can be run on one Raritan PX PDU that collects inlet current readings from other PDUs, adds that to its own inlet current reading. Then, based on a Boolean operation, executes that pre-configured load shedding on the local PDU as well as notifying the other PDUs to execute load shedding.

3.  JSON-RPC API — Instead of a LUA script on a PDU, create a script (Python/Perl/Java) that utilizes the PX API to perform the above (step 2) but run this on an element management system or CMDB or anything capable of running scripts. Just load our PX Software Developers Kit on the system where this will run.

If your racks are not configured so that a single circuit can handle a failover, it could be costly when you do have circuit failure.  Because of these 3 exclusive features of Raritan's PX line of PDUs, you are able to keep loads under a set capacity. And not just report that something bad could happen, but do something about it, before catastrophe strikes. This is just one of many unique features of the PX series of intelligent rack PDU. To learn more about other features that make your IT infrastructure more efficient click here.