Here at CBM, we have a secret to our success. Sure, you might think its having a really phenomenal product, or perhaps our stellar customer service (and, ahem, we do). But, nope. It’s really big sticky notes.
Problem to solve? Question to answer? There’s probably a big, color-coded sticky note for that, either currently adorning our walls or in our files (i.e. big pile of folded notes on the floor of various offices).
One of our conference rooms.
So, when I started to write this post about Offline VS Online units, I knew exactly where to turn. On one of my first days with the company, I was given a very comprehensive lesson complete with – you guessed it – a big sticky note.
Offline (bottom red) vs Online ( orange)
Before really digging into Offline VS Online, we should probably go over the 3 main parts of a UPS:
- Rectifier: converts AC (wall power) to DC (battery voltage)
- Batteries: reserved power
- Inverter: inverts DC (battery power) to AC (wall power)
Now, let’s go over an offline unit. In an offline unit (bottom red), most of the available power coming out of the wall goes directly to the computer (or other device the UPS is protecting), and some of the power goes through the rectifier and to the battery to keep the battery charged. The inverter is normally off. In the event of a power outage, the rectifier turns off and the inverter switches on to draw power from the battery to power to the load. The switchover time is 4 milliseconds, which is acceptable in most circumstances.
The online unit (orange), on the other hand has no switchover time, because the UPS is always online. In other words, all available power from the wall always go through the rectifier, charges the batteries, and then goes through the inverter to power the computer. If the power goes out, the rectifier simply shuts off, the battery continue to supply power to the inverter and it’s business as usual. Zero switchover time.
Besides switchover time, there are may pros and cons:
An offline unit is generally sufficient for your desktops, IP telephone systems and micro-servers. An online unit is suggested for mini-servers and anything larger.