Jargon Buster

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