Further file system improvements in Windows Server 2003 include enhancements for Network Attached Storage (NAS) and Storage Area Networks (SANs). Discussions about NAS and SANs can sometimes be confusing because they are two similar acronyms for similar technologies.
You'd think with all the letters in the alphabet that the information technology industry could come up with unique acronyms. However, to add to the confusion, both NAS and SAN are acronyms for two unrelated technologies?Network Access Server (NAS) and System Area Network (SAN). This section discusses the differences between these four technologies and then looks at the enhancements in Windows Server 2003 for Network Attached Storage and Storage Area Networks in Windows.
Network Attached Storage is a storage device that provides file share access across the network. It is essentially a file server in a box. There is even a class of NAS devices called filers, which are file server appliances. You simply plug them into the network and access the storage device via network shares as if it was a file server. Clients and servers can directly access the data stored on a NAS device across the same network. NAS devices can be used to expand storage capacity of existing file servers. The file servers map file shares to the NAS storage device. The clients connect to a share on the file server, which redirects to the NAS storage device.
Network Access Server is a method of providing authentication for access to remote networks. Generally, NAS servers are used by ISPs to provide authentication for Internet access. Network Access Servers have nothing to do with Network Attached Storage other than sharing an acronym.
Storage Area Network is a technology for connecting multiple servers and storage devices (hard drives) over a network. Generally, it consists of one or more hard drive enclosures accessed via fibre channel or Small Computer System Interface (SCSI) with partitions carved out for one or more servers, with no sharing of data between servers. To the server operating system it appears as a hard drive. Storage Area Networks are an extension of traditional high-speed direct attached storage devices, but it allows more flexibility in that it can be expanded more easily or repartitioned to more efficiently use the available storage.
A System Area Network, on the other hand, is a special technology for providing high-speed network connectivity between systems. In Windows 2000 and Windows Server 2003, Datacenter Edition, System Area Networks can be used to connect data center servers to each other using special System Area Network adapters and reliable high-speed Gigabit fibre channel connections. Additionally, System Area Networks use Winsock Direct, which provides Winsock applications direct access to the System Area Network devices without having to go through the TCP/IP protocol layer. This reduces network overhead and provides high-speed connections between servers.
Windows Server 2003 provides improvements to all these technologies. In this section we will touch on the improvements for Storage Area Networks and Network Attached Storage.
Windows Server 2003 supports "multipath failover" when connected to a SAN, which enables redundant paths from the host server." What does this mean? It means you can have multiple physical connections between the server and the storage array. If a given path (connection) fails, it dynamically uses the remaining path(s), thus providing fault tolerance for the connection between the server and SAN devices.
Windows Server 2003 also provides built-in APIs, called Virtual Disk Services (VDS), for managing SAN devices. Previously, SAN vendors had their own set of APIs for manipulating their SAN devices. So, to add more storage devices or to repartition the SAN, you had to use special applications provided by the SAN vendor. With Windows Server 2003, each vendor provides a VDS provider that translates the Windows .NET APIs to the vendor-specific APIs. VDS is an abstraction layer, which makes developing storage management applications for SANs easier because you no longer have to worry about the vendor-specific details. Therefore, SANs can be managed through the Disk Management console or command-line utilities, such as diskpart, just like any other disk.
For example, you can connect your SAN storage arrays as if they were regular disks. You can create volumes or partitions and assign them drive letters, or not?just like local disks.
Windows Server 2003 natively supports connecting to NAS devices. This support isn't immediately obvious because connecting to a NAS is implemented by simply mapping a file share, just like Windows 2000. With the native support?unlike Windows 2000?you don't necessarily need any vendor-specific applications to connect to the NAS device. The Configure Your Server Wizard can be used to install a Web-based console for configuring NAS devices. Additionally, Microsoft uses the Windows Server 2003 server operating system as the foundation for its Windows-powered NAS devices, which will be available from a number of vendors.