Easy right? Just put in a UPS (uninterruptible power supply), done, what's the big deal?... 

 

As we discussed in our February newsletter  not all UPS systems are created equal. Some lower-end models don't clean-up the AC power at all. They only protect you from power failure and surges (spikes), not much more than a cheap surge protector. There are many "dirty-power" conditions to be concerned about including  

undervoltage, line noise, frequency variation, harmonic distortion and more. Many data problems can be traced back to simply having dirty-power. 

 

Lesson: Use quality UPS power systems that give you full protection.

 

This actually sounds easier than it is. There are multiple parts in the equation providing your systems with "continuous power".

 

First let's talk about the two most common approaches, and one very important mistake to watch out for.

 

Usually two UPS units. Assuming all your devices (servers, storage, switches, etc.) have redundant power supplies you simply plug one power supply into the first UPS and the second power supply into the second UPS. If a power supply or UPS fails, you are good to go with power coming from the remaining power supply and/or UPS. This is a very common setup and works great provided you don't get caught making a very common mistake... overloading.

 

The reason UPS systems commonly get overloaded in this setup is that people don't realize that the load is automatically balancing between the two power supplies inside the device, and therefore between the UPS units. They look at the UPS meter and see that they are less than half-loaded so they keep adding more and more devices, commonly up to 80% or more. If you put a 50% load on each UPS and you lose one of them due to failure, 100% of the load goes to the surviving UPS. If both were loaded at 80%, one UPS fails and 160% load goes to the surviving UPS, which immediately overloads and fails, causing an outage losing power to the protected equipment. Of course this most commonly happens during a power outage, just when you really need your UPS units most.

 

Lesson: If you use two UPS systems, don't load them more than 50%, ideally less than 40%. Also, use devices that have redundant power inputs. If you can't plug a device into 2 (or more) power sources you really can't use this option, see option 2.

 

Most people today are familiar with RAID protection. RAID-5 for instance allows you to lose a single disk in a RAID array without losing your data. The same concept goes for N+1 UPS power systems. N+1 models are typically like a RAID system, but instead of disk drives they use multiple Power and Battery modules. By using multiple UPS Power Modules (which provide the power) and multiple Battery Modules (which provide the uptime in the event AC power is lost) you can create a highly reliable power source for your equipment or even an entire computer room, all from a single N+1 protected UPS system. These solutions are typically perceived as more expensive but in reality they are more efficient. You can easily load them to 80%+ (vs. 40% in option 1) with full protection in the event of a AC power loss, UPS Power Module failure or Battery Module failure.

 

Lesson: N+1 models are a little more expensive but provide more efficient use of space, protection and convenience.

 

By now most of us know that UPS units come with automatic shutdown software. Whether it's your desktop, server or many servers, shutdown software is included in most cases for FREE. So why do so many people not use it?

 

What happens if you don't use automatic shutdown software?

 

It's 2AM, Saturday. The power has gone out. Your critical systems are running on UPS power. You have enough battery power to keep running for 20 minutes. Assuming you even know the power is out are you going to jump in your car and rush to the office to shut everything down? Probably not. So what happens if you don't use automatic shutdown software and the power outage is longer than 20 minutes? You guessed it, all your systems crash, hard... Imagine walking up to all the systems pulling out the AC cords, you would never do that.

 

Most of the time these systems can recover, sometimes they can't. This is when you get to reacquaint yourself with that tape library and backup software you rarely touch, while spending your Sunday fixing everything...

 

So what happens if you do use automatic shutdown software?

 

It's 2AM, Saturday. The power has gone out. Your critical systems are running on UPS power. You have enough battery power to keep running for 20 minutes. The automatic shutdown software is set to do a proper shutdown if the power is out 10 minutes or longer. At 10 minutes the UPS notifies the automatic shutdown software on all the protected systems to shutdown. A shutdown command is issued, broadcast notices to your users of systems going down is sent, file systems are synced, systems shut down properly, power turns off, batteries stop being drained on the UPS systems. 2 hours later the power comes back on, the servers automatically boot back up, all the services start up and everything is back to normal. You slept like a baby and are enjoying your Sunday playing with your new iPad.

 

Lesson: You risk your data if you don't shutdown your systems properly. Use the FREE automatic shutdown software your UPS systems come with. It does take you a little more time to set it up but this could save you an immense amount of time and your data later. Quoting the Nike slogan: Just Do It!

 

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