ch is that this extra load on the server may cause server-based latency, which may be troublesome for specific applications. In network-based virtualization, the storage virtualization implementation usually depends on an in-band virtualization server (usually a Windows NT/2000 or Linux-based server) where all other network servers have to look for information about where their data actually resides. This perform- ance requirement can be very exacting on the virtualization server. Typically, these implementations run on an Intel server, which some corporate IT people generically call an NT box. Despite caching attempts by some original equipment manufacturer (OEM) vendors to minimize server latency, its bus architectures are not designed for heavy loads like the ones handled by servers that are used by very large organizations to either manage data or I/O needs. The I/O structure of Intel-based servers is usually not optimized for system configurations that require the sophisticated capabilities of set mirroring, capacity on demand, snapshot backups, or data replication. Therefore, large organiza- tions are typically very reluctant about engaging NT-based solutions in the heart of their enterprise- wide storage virtualization effort. The virtualization server remains one of the potential bottlenecks of this approach. It is often con- sidered the Achilles heel of such implementations. Some storage system companies have announced their intention to come up with hybrid virtualization offerings that would sit out-of-band without affecting the flow of data back and forth between servers and storage devices. This would seem to scale nicely for large enterprises. However, it has one big downside-virtualization software must be put on each host CPU on the network. In-band appliance-oriented virtualization is a promising approach to manage and maintain. No code is needed on host servers, and all I/O requests and responses will have to first pass through the vir- tualization engine, which essentially requires nothing else 