Back in Windows 2000 Server days, managing SAN-based storage in Windows was mostly up to your SAN vendor. You would typically need to load a tool to manage your storage device (either graphical or command-line) or sometimes use a web-based application. If you had multiple storage arrays, you would likely need to handle different user interfaces, terminologies and tools. Your experience could vary widely from vendor to vendor. At that time, centralized management of multiple networked storage solutions would be very hard, if at all possible.
That changed with Windows Server 2003, which introduced the Virtual Disk Service (VDS), a Windows service for managing volumes. Administrators now have a single interface that works with different vendors, if that vendor supplies a VDS provider for their networked storage device. This same interface also works with directly attached storage, providing a unified view of all disks and volumes, regardless of being connected via SCSI, Fiber Channel, iSCSI or PCI RAID. VDS exposes the complex functionality provided by these storage hardware vendors and scales up to enterprise configurations.
VDS, Virtual Disk Service, Windows 2000 Server, Windows Server 2003, Knowledgebase, Article