In the context of computer hardware, servers are computers that provide services to other computers and users. Servers are computers with more powerful hardware: faster CPU's, faster memory (RAM) and more of it, more disk storage space and high-speed network connections. Server operating systems specialize in providing data, services and controlling access, and frequently run other special software for handling email, file storage and communication.
Server Types
- Directory Server
- Active Directory Servers
- Windows Server 2008
- Windows Server 2003
- Windows Server 2000
- Windows NT
- LDAP Servers
- NIS/NIS+ Servers
- Active Directory Servers
- File Server
- Windows Shares
- FTP Server
- Mail Server
- Microsoft Exchange Server
- Sendmail
- Web Server
- Apache
- Microsoft Internet Information Services (IIS)
- Websphere
- Chat Server
Server Virtualization
Server Virtualization is the process of turning physical computers into simulations within software on another computer. Using virtualization, servers may be consolidated from multiple systems into fewer systems that more efficiently utilize the hardware infrastructure.
Several products are available to provide virtualization capabilities:
- Xen
- VMWare
- Microsoft Hyper-V
- Virtualbox
- Solaris Containers/Zones
Server Racks
A server rack, or just plain rack is a type of equipment rack that is a physical stand designed to allow one or more servers to be individually mounted on rails and bolted into the server rack with screws, bolts or other mounting hardware. This allows servers to be stacked vertically, saving square footage within the datacenter. Racks are mounted in rows inside a server room, datacenter, point of presence or telecom operations center to provide higher density storage of computing hardware per square foot of floor space. Conserving floor space is important, as many commercial datacenters which provide space charge by the square foot.
Rack stands may come with cable trays, power strips, surge suppressors, and even fans, depending on the needs for power, cooling, cabling and processing density.
Server Rack Types
- Cabinets
- 4-post racks
- 2-post racks (relay racks)
- Stands
Cabinets
Server rack cabinets have screened or plexiglass doors and frequently have fans at the top, bottom or both. Within the cabinets is a four-post structure supporting the ability to bolt in server rails on which to mount servers. Some designers of datacenters find cabinets with plexiglass doors more aesthetically pleasing and prefer them because they hide the cabling and buffer the noise from the equipment. One variety of cabinets provides the ability to control airflow within the cabinet, and when the airflow is managed properly, cabinets can provide cooling exactly where needed, thereby reducing power consumption by the HVAC systems and reducing the total cost of operating the datacenter. However, getting the airflow right is tricky work that takes expertise, and the design must be constantly re-evaluated as servers and support systems are swapped out and upgraded over the life of the datacenter.
4-Post Racks
Four-post server racks have four vertical metal columns with holes for bolting in rails supporting servers. There are no doors or screens on the racks and they are open to the datacenter. This provides greater ease of access for cabling, upgrades, repairs and disposal, and potentially greater airflow than is available in a closed cabinet. However, some find it aesthetically less pleasing as the cabling and the server front plates are visible.
2-Post Racks
Two post racks have a post on either side and are designed to support telecom equipment that is usually much lighter, and smaller from front to back than servers are and do not require the additional rear mounting posts for stability.
Stands
Rack stands are shelving systems that equpment is placed upon, though the term "rack stand" is often used to describe any type of equipment rack. These usually have less formal designs and often look more like desks than server racks. Many have wheels to allow the equipment to be moved easilly.
Server Rack Measurements and Standards
Rack measurement standards are outlined in the EIA-310 specification. The two most common widths for server racks in North America are the 19-inch server racks, or 23-inch server racks. Server racks can be of any height but are usually approximately 6.5 feet tall, with space at the bottom and top for cross-bracing the rack. Racks, and the servers mounted in them are measured in 'units'. One server rack unit is 1.719 inches tall and the height of the servers is measured in rack units (2U, 4U etc.).