There are three primary rack types - open-frame racks, enclosed cabinets, and wall-mount racks, each suited for different levels of security, cooling, and equipment density. Data Centers are generally large buildings with rooms that house endless racks of servers, communication equipment, storage systems, and other infrastructure elements. And sometimes it is extremely difficult to understand how all this technical diversity interacts with each other. Selecting the right rack requires evaluating its height (U), depth, width, weight capacity, airflow design, power integration. • Extended battery module increases runtime by hours. • PowerPass Distribution Module allows a step-down voltage to 120V to accommodate a variety of IT equipment. Standard Server Room equipment includes: Modern server rooms. There are three main data center topologies in use today—and each has its advantages and trade-offs. CENTRALIZED The centralized model is an appropriate topologies for smaller data. This chapter provides details about the multi-tier design that Cisco recommends for data centers. The multi-tier design model supports many web service architectures, including those based on Microsoft. NET and Java 2 Enterprise Edition.