Essential Storage Technologies

One of the few constants in Microsoft Windows operating system administration is that data storage needs are ever increasing. It seems that only a few years ago a 120-gigabyte (GB) hard disk was huge and something primarily reserved for Windows servers rather than Windows workstations. Now Windows workstations ship with 500-GB hard disks as standard equipment, and some even ship with striped drives that allow workstations to have a single 1-terabyte (TB) or larger volume that spans over several drives-and all of that data must be backed up and stored somewhere other than on the workstations to protect it. This has meant that back-end storage solutions have had to scale dramatically as well. Server solutions that were once used for enterprise-wide implementations are now being used increasingly at the departmental level, and the underlying architecture for the related storage solutions has had to change dramatically to keep up.

Using Internal and External Storage Devices

To help meet the increasing demand for data storage and changing requirements, servers are being deployed with a mix of internal and external storage. In internal storage configurations, drives are connected inside the server chassis to a local disk controller and are said to be directly attached. You'll sometimes see an internal storage device referred to as direct-attached storage (DAS).

In external storage configurations, servers connect to external, separately managed collections of storage devices that are either network-attached or part of a storage area network. Although the terms network-attached storage (NAS) and storage area network (SAN) are sometimes used as if they are one and the same, the technologies differ in how servers communicate with the external drives.

NAS devices are connected through a regular Transmission Control Protocol/Internet Protocol (TCP/IP) network. All server-storage communications go across the organization's local area network (LAN). This means the available bandwidth on the network can be shared by clients, servers, and NAS devices. For best performance, the network should be running at 100 megabits per second (Mbps) or 1 gigabit per second (Gbps). Networks operating at slower speeds can experience a serious decrease in performance as clients, servers, and storage devices try to communicate using the limited bandwidth.

A SAN is physically separate from the LAN and is independently managed. This isolates the server-to-storage communications so that traffic does not affect communications between clients and servers. Several SAN technologies are implemented, including Fibre Channel, a more traditional SAN technology that delivers high reliability and performance, and Internet SCSI (iSCSI), a newer SAN technology that delivers good reliability and performance at a lower cost than Fibre Channel. As the name implies, Internet SCSI uses TCP/IP networking technologies on the SAN, allowing servers to communicate with storage devices using the IP protocol. The SAN is still isolated from the organization's LAN.