vice to remote or hosted sites is lost. For this reason, organizations might lease Internet access from more than one carrier with each carrier running its service into a different part of the building to pre- vent total loss of network access if cables in the same conduit are cut. Alternatively, an organization can lease a wireless broadband access connection to prevent service inter- ruption in the event of a cable failure. (For more information, see Chapter 7, "Mobile and Wi-Fi Networks.") Environmental Controls in Data Centers Virtualization has decreased the number of physical servers needed in data centers. However, each physical server requires more cooling due to its more powerful, quad processors that generate more heat than dual or single processors. In addition, electric- ity costs needed for cooling are increasing dramatically. Designing cooling, power, and Uninterrupted Power Supply (UPS) systems that distribute power are SO complex that organizations often hire consultants to design Next-Generation Data Centers: Virtualization and Gigabit Speeds Automatic Failover (Backup) to a Remote Site Using Replication Software in Virtualized Servers Headquarters site Remote, backup site Ethernet LAN Ethernet LAN Physical host Physical host server with servers virtual machines Servers at headquarters with replication software and virtual machines ######## ******** ******** HE: ******** ******** ######## HE! LITTLE ******** ******** ******** HE: Switch Switch Switch WAN = Wide Area Network LAN = Local Area Network SAN = Storage Area Network Figure 2-3 Automatic failover to a remote site. cost-effective environmental controls. The number of people in the data center will further impact cooling needs. In addition, there are different cooling requirements for equipment located at the bottom of racks versus equipment located at the top. The type and amount of lighting will also impact cooling requirements. IBM, EMC, and HP are among the companies that offer energy consulting services aimed at designing cost- effecti