n Storage Area Network (SAN)
A SAN is a high-speed special-purpose network (or subnetwork) that interconnects different kinds of data storage devices with associated data servers on behalf of a larger network of users. Typically, a storage area network is part of the overall network of computing resources for an enterprise. A storage area network is usually clustered in close proximity to other computing resources such as IBM S/390 mainframes but may also extend to remote locations for backup and archival storage, using wide area network carrier technologies such as asynchronous transfer mode or Synchronous Optical Networks. A storage area network can use existing communication technology such as IBM’s optical fiber ESCON or it may use the newer Fibre Channel technology. Some SAN system integrators liken it to the common storage bus (flow of data) in a personal computer that is shared by different kinds of storage devices such as a hard disk or a CD-ROM player. SANs support disk mirroring, backup and restore, archival and retrieval of archived data, data migration from one storage device to another, and the sharing of data among different servers in a network. SANs can incorporate subnetworks with network-attached storage (NAS) systems.

n Direct Attached Storage (DAS)
Direct Attached Storage is a storage device that connects directly to a single server. In order for clients on the network to use the storage device they must have access to the server it is connected to. In addition to handling the storage and retrieval of data files the server will also handle applications such as e-mail or databases. The result is that performance of direct storage is not as high as that of networked storage. However on a small scale direct storage is much simpler to administer since you only have to deal with one server connected to the storage device.

n Clustering
In computers, clustering is the use of multiple computers, typically PCs or UNIX workstations, multiple storage devices, and redundant interconnections, to form what appears to users as a single highly available system. Cluster computing can be used for load balancing as well as for high availability. Advocates of clustering suggest that the approach can help an enterprise achieve 99.999 availability in some cases. One of the main ideas of cluster computing is that, to the outside world, the cluster appears to be a single system. A common use of cluster computing is to load balance traffic on high-traffic Web sites. A Web page request is sent to a "manager" server, which then determines which of several identical or very similar Web servers to forward the request to for handling. Having a Web farm (as such a configuration is sometimes called) allows traffic to be handled more quickly. Clustering has been available since the 1980s when it was used in DEC’s VMS systems. IBM’s sysplex is a cluster approach for a mainframe system. Microsoft, Sun Microsystems, and other leading hardware and software companies offer clustering packages that are said to offer scalability as well as availability.

n Online Transaction Processing (OLTP)
OLTP is a class of program that facilitates and manages transaction-oriented applications, typically for data entry and retrieval transactions in a number of industries, including banking, airlines, mailorder, supermarkets, and manufacturers. Probably the most widely installed OLTP product is IBM’s CICS (Customer Information Control System). Today’s online transaction processing increasingly requires support for transactions that span a network and may include more than one company. For this reason, new OLTP software uses client/server processing and brokering software that allows transactions to run on different computer platforms in a network.

n Blade Server
A blade server is a thin, modular electronic circuit board, containing one, two, or more microprocessors and memory, that is intended for a single, dedicated application and that can be easily inserted into a space-saving rack with many similar servers. One product offering, for example, makes it possible to install up to 280 blade server modules vertically in multiple racks or rows of a single floor-standing cabinet. Blade servers, which share a common high-speed bus, are designed to create less heat and thus save energy costs as well as space. Large data centers and Internet service providers (ISPs) that host Web sites are among companies most likely to buy blade servers.

A blade server is sometimes referred to as a high-density server and is typically used in a clustering of servers that are dedicated to a single task, such as:

l file sharing
l Web page serving and caching
l SSL encrypting of Web communication
l transcoding of Web page content for smaller displays
l Streaming audio and video content

Like most clustering applications, blade servers can also be managed to include load balancing and failover capabilities. A blade server usually comes with an operating system and the application program to which it is dedicated already on the board.

n Consolidation
Physical consolidation entails the co-location of multiple platforms at fewer locations. This could be as simple as centralizing servers in fewer physical locations, by spotting opportunities to reduce the total number of servers—looking for overlapping hardware and software functionality. This kind of consolidation can help to simplify management, save on personnel and reduce TCO, because companies end up having to license fewer instances of expensive server software. The benefits of consolidation depend on which approach is deployed, but may include: Reduced costs and increased organizational efficiency. However, many server consolidation projects miss the mark entirely, yielding little or no benefit—and sometimes incurring costs rather than offering savings