Issue link: https://cp.revolio.com/i/809568
10 | THE DATA CENTER JOURNAL www.datacenterjournal.com a s we increasingly rely on digital devices, more and more information is loaded on servers all around the world. ese servers have volatile memory (nonpermanent memory) that they use to perform calculations and do trans- actions. Use of this type of memory is faster and cheaper than trying to access and store data from permanent memory (hard drives). When the pro- cessing is done, groups of data from volatile memory are transferred onto hard drives in batches. Now, what happens when a server experiences a power outage without backup power? e server will abruptly shut down and all the data that was in volatile memory will be lost, since it wasn't in permanent memory. You may ask, "Don't server farms have backup generators that are meant to maintain power?" Most do and can provide backup power when an outage occurs, but the generators take time (minutes) to detect an out- age and turn on. By that time, the data may already be lost. no data left BehInd Most backup solutions in data- storage systems have one of two goals: 1. Ensure that enough energy is available to continue running the system until backup generators are operational. 2. Ensure that enough energy is available for any data in volatile memory to be transferred into non- volatile memory, then gracefully shut down the system. In the server industry, the quick transfer of data from cache to permanent memory is sometimes called a fire-hose dump. Figure 1 details the flow. Several solutions provide backup power for servers, and we will discuss three of them before looking at the performance characteristics of each one as it relates to data storage. Backup power optIonS for data Storage Supercapacitors. Recent ad- vances in flash memory have allowed supercapacitors to act as a backup power source. e write time to flash memory is much faster than to hard drives, allowing low-energy options with high current capability to act as a backup option. at is where superca- pacitors come into play. ese devices have very high capacitance that can create a huge amount of discharge current. Supercapacitors are serving in data servers where the uptime re- quirement is very small (seconds), but a high amount of power is required. lead-acid batteries. For many years, lead-acid batteries have been the cornerstone technology for backup applications. ey have a very cost-effective unit price relative to other technologies and offer good performance. Many UPS (uninter- ruptable power supply) units contain lead-acid batteries; they appear in backup servers and computer systems. lithium-ion batteries. Li-ion batteries are becoming more popular as a backup solution for many serv- ers, especially those that require a lot of energy and power to back up the system. Figure 1. Fire-hose dump during a power outage.