. Power cuts and interruptions, fire, and natural disasters such as hurricanes all have the potential to shut down computer operations. Human error is also a common cause of failures. Data centers are often located in out-of-the way spaces within buildings, particularly if there is a shortage of office space. Thus, it's not uncommon for data centers to be located in basements. In low-lying areas this is a problem because of the danger of flooding the data center and destroying the equipment. Although most data centers have raised floors, floods in these areas are nevertheless a problem. Enterprises and carriers with mission-critical data centers must decide where to spend money on redundancy and protection from catastrophic failures. See Figure 2-4 for an example of failover during a data center failure. Because loss of an uninterrupted power supply can bring down a data center, many organizations consider redundant UPS and backup electric generator service. This can mean two UPS's and backup generators connected to the same electrical feed or the more costly option of two electrical feeds, each with its own UPS. Organizations with two electrical feeds generally arrange that each enter the building in separate conduits and separate building entrances. If one electrical cable is cut, the data center will fail over to the other one. This is expected of hosting and cloud providers and other critical infrastructure suppliers. Automatic Failover (Backup)to a Remote Using Replication Software in Virtualized Servers www.TechnicalPDF.com Headquarters site Remote, backupsite Ethernet LAN Ethernet LAN Physical host Physical host server with servers virtual machines Servers at headquarters with replication software and virtual machines LAAAL am Figure 2-4 Automatic failover to a remote site. An even more costly option is to lease or build a second, backup data center. The backup may be at a providers' site or may be owned and operated by the enterprise. Storage Systems-Managing Petabytes of Data Organizations use storage sy