PeteDotCom -> Networking -> Misc -> Volumes ->   Ok a quick break down of Volumes: Both Windows NT Server and Windows NT Workstation can create and use volume sets. Volume sets provide no fault tolerance; if even one area of disk space in the set is lost, all the data is lost. Volume sets are transparent to the user. When a volume set is created all areas of free space are assigned the same drive letter. Volume sets are the only Windows NT disk partition management option that allows more than one area of disk space in the set to reside on the same physical hard disk. Volume sets are the only Windows NT disk partition management option that allows the individual areas of disk space making up the volume to be of different sizes. Creating Volume Sets: Volume sets must be created from free disk space--they cannot be used with existing partitions. To create a volume set, first select free space on 1 to 32 disks, then select Create Volume Set from the Partition menu in Disk Administrator. Shut down and restart the computer. When Windows NT restarts, Autochk.exe will run the equivalent of "chkdsk /f" on the entire volume set and the volume set will be created or extended. You can then format it for a file system. Volume sets are file system independent and can be formatted with any hard disk file system installed with Windows NT. Volume sets can be created on 1 disk or as many as 32. Configuration Characteristics Normally, only the Windows NT installation that created the volume set will recognize it--other operating systems will not. MS-DOS will identify the different areas of disk space in the volume set as "Non- DOS." From within other Windows NT installations, Disk Administrator will identify the areas of disk space in the volume set as having an "Unknown" file system. Other installations of Windows NT on the same computer can recognize a volume set created by a different installation of Windows NT by restoring disk configuration information. See page 529 of the "Windows NT Advanced Server System Guide" for more information. You cannot install Windows NT on an existing volume set. Setup describes volume set partitions as "Windows NT Fault Tolerance." If you attempt to select one of these partitions for installation, a message states that Windows NT does not recognize this partition, and you must delete it before Setup can use it.  Volume sets may offer somewhat better performance than input and output from a single partition, but their main advantage is that they allow the most efficient use of hard disk space. The small print - (Source Microsoft.com, edited by my self)