 such challenge is managing memory in the host physical servers. Operating systems Data Centers and IP Private Branch Exchanges installed on host servers now have more code and require more memory to operate. IT staff members allocate memory to applications on virtual machines by using VMware's Hypervisor software. Staff members need to monitor applications' memory usage SO that servers can be upgraded or applications moved to other hosts if memory in the cur- rent host is not adequate. If this isn't done, applications will run slowly and response times on individual user computers will be degraded. New servers are equipped with quad CPUs-quite literally, four CPU chips on a single host server. However, as the amount of processing needed to run programs grows, even this is not always adequate for the virtual machines installed on them. Programs that have sound and video are "fatter," with more code, which requires addi- tional CPU overhead. It's difficult to estimate under these conditions the amount of CPU power that's required for applications running on virtual machines. In addition, disk storage is being used up at a faster rate. Users now routinely store MP3 files in their e-mail inboxes. In data centers where user files and e-mail messages are archived, this can deplete spare storage in Storage Area Networks (SANs) at a faster rate than planned. Thus, storage, memory, and processing requirements should be monitored. In large, complex data centers, it can sometimes be easier to monitor and manage single physical servers rather than virtual machines and storage. In small organizations, managing memory, storage, and CPU usage is not as com- plex. With only one or two physical servers, it's not as difficult to track and manage resource allocation. Server Sprawl Server sprawl is the unchecked proliferation of virtual machines on physical host servers. (Virtual machines are also referred to as images.) Managing server sprawl in large data centers is a major challenge. Because it's easier to install applications o