A hardware device, commonly referred to as a NAS box, acts as the interface between storage and clients on the network. The NAS box requires no mouse, keyboard, or monitor, and is controlled by a remote client over the network. A bare-bones embedded operating system - typically Linux-based - runs on the NAS, although the latest devices also provide a front-end interface that makes setup and administration over your network easier (again, similar to Windows Home Server).
You can purchase a simple NAS box with a single 1TB drive, such as Seagate’s BlackArmor NAS 110, for less than $200, with prices rising rapidly as you add capacity, expandability, and other features. If all you need in a server is a device for sharing files, gaining remote access, automatically backing up client PCs over the network, or hosting IP security cameras, one of these budget models will fit the bill. At the other end of the scale, you’ll find devices such as Synology’s RS3412xs ($4,000 plus, not including the drives), a rack-mount NAS device that can host up to 10 hard drives and even supports virtualisation.
Tower servers (and their smaller cousins, micro towers) are the first step up from a NAS. You can easily mistake a tower server for a desktop PC - and in fact, you can press a desktop PC into service as a server. Tower servers cost more than NAS products, but they’re much less expensive than rack-mount systems. They can operate on the floor or on top of a desk, but you can also retrofit them to sit in a rack. Tower servers are generally quiet, because they don’t require a lot of cooling fans. A high-end tower server with a fast CPU, lots of RAM, and a plethora of hard drives can pack a punch, especially when you take virtualisation into account (provided that the CPU and operating system support it).
On the downside, you’ll need a keyboard, monitor, and mouse to manage each tower server, or you can invest in a KVM (keyboard, video, mouse) option that enables one set of peripherals to control several machines. (You can control micro towers running Windows Server using Remote Desktop Connection via a client PC.) More important, a tower server provides limited scalability once you’ve maxed out its capabilities. If you anticipate your IT requirements expanding rapidly, a rack or blade server is a better alternative than finding space for a bunch of towers.
Tower servers come with the same operating system choices as rack and blade servers do, including various flavors of Windows Server and Linux. Prices range from $350 for an HP ProLiant MicroServer with 2GB of RAM and a 250GB hard drive (expandable to four 2TB drives) running Windows Server 2008 R2 Foundation to $2,500 for a Dell PowerEdge T710 tower server with an Intel Xeon CPU, 4GB of memory, and a single 500GB hard drive. Be aware that not all tower servers include the price of an operating system.
If you anticipate the need to run several servers, either right away or in short order, consider moving up to rack-mount models. These types of servers come in a standard width (to fit in a 19-inch rack) and a standard height (a multiple of 1.75 inches, or 1U; a standard rack is 42U high). A rack permits you to fit many servers into a relatively small footprint, and typically it includes a cable-management system to keep your installation neat.
Most rack servers are highly expandable, with sockets for multiple CPUs, copious amounts of memory, and lots of storage. Rack-server systems are highly scalable, too; once you have the rack in place, you won’t need floor space for additional servers until the rack is full. Although they typically cost more than tower servers, they’re cheaper than blades.