PRIMER

Servers Simplified

Server Operating Systems

Server operating systems are intended to provide and manage access to network resources, such as shared files and the Internet. Because of the need to manage access for multiple users, desktop operating systems aren't suitable for servers; they're intended to provide an interface for one person to run end-user applications.

Common server operating systems include:

• Microsoft Windows Server;


• Microsoft Small Business Server;


• various kinds of Linux; and,


• other alternatives such as AIX and UNIX.

Servers are often priced both with and without operating systems. Smaller businesses with a minimal IT staff typically elect to have the vendor install the operating system.

With Windows Server, the most popular server operating system, the standard price covers five users. Additional CALs (client access licenses) can be purchased either on the basis of named users or connected devices. The cost for each additional user or device is generally between $30 and $40.

Server Storage

Servers typically have multiple hard drive bays, for future expansion, as well as removable media. By contrast, desktop PCs usually have one hard drive, plus removable media such as a DVD drive. Server hard drives typically employ the latest data transfer technology such as SAS (Serial Attached SCSI) and SATA (Serial ATA.)

Servers with multiple hard disks and controllers that support redundancy can be configured as RAID (Redundant Arrays of Independent Disks) systems. RAID configurations distribute data across multiple hard drives to speed access by as much as a third and protect against data loss.

For office servers, the most common RAID configurations are RAID 0, which allows faster data access, and RAID 1, which allows automatic disk mirroring; meaning that the contents of one disk are automatically copied on another. Other configurations less common to office servers are RAID 5 and RAID 6. Mirrored RAID configurations reduce the amount of available storage to less than the total physical hard disk space. In all configurations, RAID systems appear to the microprocessor as a single hard drive.

Another option on high-end servers is hot-swappable drives, allowing hard drives to be removed or added without turning off the server.

Server Input and Output

Most desktops PCs now have a built-in Ethernet port to connect to other computers. Servers have two ports, so that one can "fail over" to the second if it encounters a problem and to allow for shared Internet connections. Sever ports are also higher speed -- 1Gbps rather than 100Mbps -- to accommodate connection to network storage devices.

Server operating systems perform many tasks through command line interfaces (remember DOS?), rather than the graphical interfaces common to desktop PCs. Office servers also don't need powerful graphics cards -- video games don't run on office servers typically -- and have not sound card or speakers.

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