Modern data center server racks and cabinets often have multiple power inputs, which allow you to draw power from multiple sources at once. While it is not always commonplace to do so, one may wonder if it’s worthwhile to take advantage of this technology. Would it be most efficient for one of them to flow from the grid while the other flows from a UPS? What about two UPS’s?
Voltage and amperage fluctuations are much more likely to occur on grid power, but their affects would be minimal. However, there are a lot of other events that affect the grid in larger ways that could potentially damage systems. For instance, brownouts tax the grid heavily and cause massive fluctuations. Voltage spikes also commonly occur when current from nearby lightning strikes finds its way into the mains. With the kind of unpredictability that can be caused by all of the various natural events that affect grid power, some form of precaution to protect your gear will undoubtedly seem like a good idea.
Of course, in this case, one of the first things to come to mind is the UPS (uninterrupted power supply), however the UPS is not the end-all solution in this case. This is because they all eventually fail, and when they do, the consequences can be catastrophic to your racks of storage systems. It is much more likely in these scenarios that the UPS will instead simply stop holding a charge, which won’t destroy your system. Rather, this would simply turn the UPS into a simple power strip. Another fault worth considering is their low tolerance for overloading. If you ever attempt to draw more from a UPS than it is rated for, it will overheat and potentially cause real issues. Even in a best-case scenario where power goes out and the UPS must kick in to support the system, most of them only supply about an hour of uptime depending on how power hungry your data center equipment is.
So does this all mean that you are better off trusting the grid power after all? Hardly. The point is that every system has its flaws, so you never want to put all of your faith in just one solution. Rather, the idea as you might have guessed, is to use both options. This is because, in the long run, the likelihood of both sources of power going down simultaneously is very low. One effective, extra measure of protection can be taken by conditioning the power coming from the grid with a high-quality PDU that features a surge protector. These are relatively cheap, and do a good job of smoothing out grid power and lessening your chances of catastrophic system damage.