One of the most important foundational elements of your data center is reliable power. This becomes even more important when your data network is carrying both data and voice – essentially all of your business communication. This is where failure is really not an option.
In years past, the only way to get high-availability UPS power was to have a primary and secondary UPS. This was referred to as a “2N” design, that is there needed to be twice the number of UPS units to accommodate a primary and secondary UPS.
Unfortunately, the 2N design required you to spend double the number of UPS units (at the same time doubling your cost) and it also meant that, most of the time, your UPS would be utilized at less than 50%. This resulted in increased operational cost as the UPS units never ran anywhere close to full utilization, where they run most efficiently.
You may also be familiar with the dual-UPS-in-every-rack design. This approach had a number of additional drawbacks because it took up a significant amount of precious rack space for UPS units and even more rack space if extended run batteries were used. Since the external batteries could not be shared between the UPS units, this results in (again) doubling the number of batteries to achieve redundancy. Because the UPS units were typically dedicated to serving only the equipment in the same rack that they were in, any unused capacity was usually was unavailable to equipment in other racks that needed it.
You can see how, very quickly, this design can get out of hand from both a data center real-estate as well as a cost perspective. But there is a better way to achieve high availability power without breaking the bank or giving up 1/3 of your rack space.
N+1 Redundancy vs 2N Redundancy
The APC Symmetra product line utilizes N+1 redundancy which is a far more efficient architecture.
If you are familiar with RAID-5 technology for hard drives, you have seen this technology before. The Symmetra N+1 technology is effectively RAID-5 for power. Here’s how it works:
The Symmetra UPS is modular. It utilizes multiple power modules in a single UPS chassis. You can think of a power module as an inverter that converts DC power from the batteries into AC power for your equipment. Each of the power modules can work together and share the load. In an N+1 configuration, the UPS employs one more power module than is needed to carry the load. For example, a load of 6KVA could be carried by two 4KVA power modules with each power module carrying 3KVA. By adding a third power module, the load is split among all three power modules with each power module carrying 2KVA. If one of the power modules should fail, the load is shared between the remaining power modules (in this case, the two remaining operational power modules would now carry 3KVA each).
The UPS chassis also has a primary and backup intelligence module (essentially the brainpower of the UPS) to help eliminate single points of failure in the unit.
Note that with an N+1 design, we only increase the number of additional power modules by one unit. We do not have to utilize two entire UPS units, nor do we need to double the number of batteries. This results in significant reduction in the amount of real estate used in the data center and even more importantly, can significantly reduce cost. Because we have consolidated UPS power, we can now send power to any rack that needs it – simply by running an additional rack PDU (Power Distribution Unit – aka “Plug Strip”) to that rack.
Hot-Swappable Components
In the case of a power module failure, intelligence module failure, or battery failure, the system supports simple, hot-swappable replacement. Unlike the days when you had to wrestle with disconnecting connectors, these Symmetra components slide out the same way that you slide a drawer out of a desk. New units slide in the same way – all without any downtime!
Modularity = Pay-as-you-Grow
Another advantage to the modular Symmetra design is that you don’t have to oversize your UPS to account for possible future growth. You simply choose the right UPS chassis and add only the power modules and battery modules that you need to start with and add additional power modules if, and when, you need them. This means that you can operate the UPS at a higher utilization percentage which translates to higher efficiency(converting less unused energy into heat within the UPS). This also helps reduce operational costs.
Symmetra UPS units enable you to save money in generator costs
Because Symmetra units utilize Double-Online Conversion they are able to be powered from a generator that is only 50% oversized (varies by model) vs %300 to %500 oversized for SmartUPS which utilize Line-Interactive Conversion technology. This can add up to some significant cost savings in generator costs alone.
These are just some of the very compelling reasons to use APC’s Modular Symmetra N+1 technology to power your data center equipment.