cal host servers by using a uniform software package. It hopefully also eliminates some of the finger pointing in problem diagnostics, for which technicians are not certain if the problem is in the network or in equipment or software. Some examples include the following. Cisco Systems, Inc., EMC Corporation, and VMware, Inc. (which is owned by EMC) have created a coalition to collaborate on networking, virtualiza- tion, and storage equipment. Hewlett-Packard (HP) purchased 3Com to expand its switching line. HP also purchased LeftHand to offer customers its virtualized storage arrays, aimed at small and midsize organizations. Juniper Networks, Inc., has original equipment manufacturer (OEM) partnerships with Dell and IBM Corporation. An OEM agreement enables vendors to put their own brand name on equipment developed by another manufacturer. Using Storage Area Networks for Backing Up Computer Files Storage Area Networks (SANs) are used by organizations to archive backup copies of computer files and databases on specialized computers. The files and databases are stored locally, usually at another one of the organization's sites, or at a site managed by a third party. Thus, in the event of a computer failure or natural disaster, files can be recovered. Frequently, only the changes in files are backed up nightly by using spare capac- ity in data lines. As LANs and WANs became more powerful, SANs began using disk mirroring to back up files in real time. Disk mirroring is the process of simultaneously writing data to backup and primary servers SO that all recent changes are saved and up- to-date, in the event of a failure. Data Centers and IP Private Branch Exchanges SANs in Data Centers Additionally, SANs are an integral part of the day-to-day data center operations. Hard drives used for storage have become smaller and more powerful, and are arranged in denser configurations. Small disk drives can be networked together in arrays SO that they appear as one disk to the network. These arrays are referred to as Redundant A