New appliances provide an alternative to typical Fibre Channel and iSCSI approaches. Running virtual machines on network file systems (NFS) provides a number of architectural advantages, starting with the fact that virtual machines use files to store their image information. Since network-attached storage (NAS) systems are built from the ground up for file management, the administrative time and resources to oversee a large number of virtual machine files is less than what is required to manually assign and place those files on individual logical unit numbers (LUNs).
New offerings, such as scalable caching appliances, now allow customers to extract more performance out of their existing NAS and NFS infrastructure. In fact, there are environments where NFS can perform as fast, if not faster, than other storage solutions based on Fibre Channel or iSCSI. By deploying NAS and NFS storage solutions, administrators can forgo many of the complexities associated with maintaining separate Fibre Channel adapters, switches and storage systems.
The necessity of Fibre Channel adapters is also one of the biggest problems in virtual environments, since rack-mounted servers often have a limited number of slots available for adapter cards. An Ethernet and IP-based solution avoids excessive adapters and can make effective use of embedded Gigabit Ethernet ports on the motherboard.
When provisioning virtual disks with NFS, new data stores can be added quickly by mounting a file system. There is no need to create or provision LUNs, as is the case with Fibre Channel or iSCSI data stores. In addition, some NFS systems allow for expanding and decreasing NFS volumes on the fly, and incorporate thin provisioning features by default, saving disk space. Users also can provision new virtual disks from an NFS snapshot, allowing rapid deployment of new virtual disks from a copy/snapshot of an existing virtual disk.
Managing virtual disks is typically...

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