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Started by dhilipkumar, Sep 13, 2008, 05:23 PM

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Sep 13, 2008, 05:23 PM Last Edit: Sep 28, 2008, 12:36 AM by dhilipkumar
What is Green computer ?

             "The computer must be designed to use only non-toxic materials, to be energy efficient, and to have minimal impact on the environment in every stage of its life cycle." Elaborating on the last point, she adds: "A recycling strategy should be considered part of the computer's design, e.g., the computer should be designed for easy disassembly and disposal or made so that it is safe to discard."

The next environmental trend is "green IT". Computers may not produce plumes of smoke but they do consume surprisingly large amounts of electricity.

The computer industry is responsible for almost 2% of global carbon emissions, according to technology research group Gartner, mainly from PCs, servers and cooling systems.

            Google has more than 500000 servers in 40 data centres. It has never revealed how much greenhouse gas it generates, but the global Internet company says it now offsets this through a mixture of renewable energy, increased energy efficiency and other projects.

             Google is not alone in switching to green IT. SA companies are close behind in finding more energy-efficient ways of minimising the effect of technology usage on the environment.


what is Blu-ray ?

              Blu-ray is an optical disc format designed to display high definition video and store large amounts of data.

Blu-ray is the successor to DVD. The standard was developed collaboratively by Hitachi, LG, Matsushita (Panasonic), Pioneer, Philips, Samsung, Sharp, Sony, and Thomson. It became the default optical disk standard for HD content and optical data storage after winning a format war with HD-DVD, the format promoted by Toshiba and NEC.

The format's name comes from the fact that a blue laser reads from and writes to the disc rather than the red laser of DVD players. The blue laser has a 405 nanometer (nm) wavelength that can focus more tightly than the red lasers used for writable DVD. As a consequence, a Blu-ray disc can store much more data in the same 12 centimeter space. Like the rewritable DVD formats, Blu-ray uses phase change technology to enable repeated writing to the disc.

Blu-ray's standard storage capacity is enough to store a continuous backup copy of most people's hard drives on a single disc. Initially, the format had a 27 gigabyte (GB) single-sided capacity and 50 GB on dual-layer discs. Single-sided Blu-ray discs can store up to 13 hours of standard video data, compared to single-sided DVD's 133 minutes. In July 2008, Pioneer announced that they had found a way to increase capacity to 500 GB by creating 20-layer discs. These discs are not, however, expected to be commercially available in the near future.



Hi Dhilip

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   What is RAID?

        RAID (redundant array of independent disks; originally redundant array of inexpensive disks) is a way of storing the same data in different places (thus, redundantly) on multiple hard disks. By placing data on multiple disks, I/O (input/output) operations can overlap in a balanced way, improving performance. Since multiple disks increases the mean time between failures (MTBF), storing data redundantly also increases fault tolerance.

A RAID appears to the operating system to be a single logical hard disk. RAID employs the technique of disk striping, which involves partitioning each drive's storage space into units ranging from a sector (512 bytes) up to several megabytes. The stripes of all the disks are interleaved and addressed in order.

In a single-user system where large records, such as medical or other scientific images, are stored, the stripes are typically set up to be small (perhaps 512 bytes) so that a single record spans all disks and can be accessed quickly by reading all disks at the same time.

In a multi-user system, better performance requires establishing a stripe wide enough to hold the typical or maximum size record. This allows overlapped disk I/O across drives.

There are at least nine types of RAID plus a non-redundant array (RAID-0):

RAID-0: This technique has striping but no redundancy of data. It offers the best performance but no fault-tolerance.

RAID-1: This type is also known as disk mirroring and consists of at least two drives that duplicate the storage of data. There is no striping. Read performance is improved since either disk can be read at the same time. Write performance is the same as for single disk storage. RAID-1 provides the best performance and the best fault-tolerance in a multi-user system.

RAID-2: This type uses striping across disks with some disks storing error checking and correcting (ECC) information. It has no advantage over RAID-3.

RAID-3: This type uses striping and dedicates one drive to storing parity information. The embedded error checking (ECC) information is used to detect errors. Data recovery is accomplished by calculating the exclusive OR (XOR) of the information recorded on the other drives. Since an I/O operation addresses all drives at the same time, RAID-3 cannot overlap I/O. For this reason, RAID-3 is best for single-user systems with long record applications.

RAID-4: This type uses large stripes, which means you can read records from any single drive. This allows you to take advantage of overlapped I/O for read operations. Since all write operations have to update the parity drive, no I/O overlapping is possible. RAID-4 offers no advantage over RAID-5.

RAID-5: This type includes a rotating parity array, thus addressing the write limitation in RAID-4. Thus, all read and write operations can be overlapped. RAID-5 stores parity information but not redundant data (but parity information can be used to reconstruct data). RAID-5 requires at least three and usually five disks for the array. It's best for multi-user systems in which performance is not critical or which do few write operations.

RAID-6: This type is similar to RAID-5 but includes a second parity scheme that is distributed across different drives and thus offers extremely high fault- and drive-failure tolerance.

RAID-7: This type includes a real-time embedded operating system as a controller, caching via a high-speed bus, and other characteristics of a stand-alone computer. One vendor offers this system.

RAID-10: Combining RAID-0 and RAID-1 is often referred to as RAID-10, which offers higher performance than RAID-1 but at much higher cost. There are two subtypes: In RAID-0+1, data is organized as stripes across multiple disks, and then the striped disk sets are mirrored. In RAID-1+0, the data is mirrored and the mirrors are striped.


What is VHDL?

                 VHDL (VHSIC Hardware Description Language) is a computer programming language designed to illustrate the behavior of field-programmable gate arrays and application-specific integrated circuits of digital systems in electronic design. VHDL describes the performance of electronic components in many areas such as; microprocessors, custom chips and simple logic gates. VHDL is used to describe precise aspects of electrical circuit behavior in order to create a VHDL simulation model. Incorporated with schematics, block diagrams and system-level VHDL descriptions, the VHDL simulation model can be used as the foundation for building larger circuits.

           Additionally, VHDL functions as a general-purpose programming language. VHDL has similarities to the C and C++ programming language structure. VHDL differs in that it includes features that allow simultaneous events description and provides a solid set of control and data representation features. VHDL is primarily used to detail the performance specification of a circuit in the form of a test bench. These circuit stimuli and comparable expected outputs substantiate the functionality of a circuit over the course of a period of time.

           An information technology professional interested in learning more about VHDL can participate in the informative tutorials provided in this section.


what is AJAX:

        “Asynchronous JavaScript And XML”, otherwise known as AJAX, is a programming language that allows a web page to receive miniscule amounts of data from a web server without reloading the complete web page. Ajax works together with JavaScript. AJAX permits Web pages to be dynamic, interactive and behave as local applications. This combination of features is known as “rich client” applications. AJAX is similar to Dynamic HTML and allows synchronous and asynchronous access to remote services by using the XMLHTTPRequest object.

          Before AJAX technology was developed, a request from the user for the retrieval of data would cause the entire Web page to be refreshed, resulting in very slow loading time and minimal interaction between the user and the web page. With the advent and success of AJAX, websites utilize the “remote scripting” of AJAX to better the functionality and waiting time of interactive and dynamic websites. The server exchanges small amounts of data without the user’s knowledge, increasing the speed, usability and navigation of web pages.

It is necessary for any IT professional programmer or developer to be familiar with the Ajax programming language. Online Training explaining the uses of Ajax, critique of Ajax, Challenges, Framework, basic overview of Web Services, XML, security aspects and the power of Ajax are discussed through tutorials in this section.


What is N-Tier?

N-Tier applications are useful, in that they are able to readily implement Distributed Application Design and architecture concepts. These types of applications also provide strategic benefits to solutions at the enterprise level. It is true that two tier, client server applications may seem deceptively simple from the outset â€" they are easy to implement and easy to use for Rapid Prototyping. At the same time, these applications can be quite a pain to maintain and secure over time.

N-Tier applications, on the other hand, are advantageous, particularly in the business environment, for a number of reasons.

N-Tier applications typically come loaded with the following components:

Security. N-Tier applications come with logging mechanisms, monitoring devices, as well as Appropriate Authentication, ensuring that the device and system is always secure.

Availability + Scalability. N-Tier applications tend to be more reliable. They come loaded with fail over mechanisms like fail over clusters to ensure redundancy.

Manageability. N-Tier applications are designed with the following capabilities in mind: deployment, monitoring, and troubleshooting. N-Tier devices ensure that one has the sufficient tools at one’s disposal in order to handle any errors that may occur, log those errors, and provide guidance towards correcting those errors.

Maintenance. Maintenance in N-Tier applications is easy, as the applications adopt coding and deployment standards, as well as data abstraction, modular application design, and frameworks that enable reliable maintenance strategies.

Data abstraction. N-Tier applications make it so that one can easily adjust the functionality without altering other applications.


Data Modeling

      Information systems and computer sciences use data modeling to manage and organize large quantities of structured and unstructured data. A data model describes the information to be stored in vast data management systems like relational databases. Data models do not include unstructured data such as email messages, word processing documents, digital video, audio or image files. Furthermore, data modeling establishes implicit and explicit constrains and limitations of the structured data. A data model is formally known as data model theory.

A professional Information Technologies engineer may work as a Data Modeling Analyst for businesses using enterprise data management tools and technologies. A Data Modeling Analyst or Data Model Manager will be familiar with process modeling, understanding data modeling concepts, data modeling tools, entity relationship diagramming, dimensional data modeling and physical or logical data modeling.

Data Modeling Analysts use data modeling functions to supply an accurate representation of the enterprise. Secondly, data modeling is used to accurately reflect the data of the organization. Based on this information, a database is created.

Tutorials on Data Management in Data Modeling explain the basic concepts behind data modeling, its uses with enterprise management, terminology related to data modeling, the history of data modeling and instructions on various models within data modeling.


Thanks for your informative article...Proud Acumen...continue.....


What is 3x Protocol

3x is the second revision of the Evolution-Data Optimized (EV-DO) set of mobile telecommunications standards made by the Third Generation Partnership Project 2 (3GPP2). It is also known as TIA-856 Rev B or EV-DO Rev B, antecedent to EV-DO Rev 0 and EV-DO Rev A.

It is one of several types of the CDMA2000 set of standards, its full designation being CDMA2000 3xRTT, where "3xRTT" stands for "three times Radio Transmission Technology" (three times because it has three carriers, in comparison to 1xRTT which has only one carrier).

The 3x protocol, like all other EV-DO standards, is a form of 3G technology. In order to maximize its rate of data transmission, 3x makes use of varied multiplexing techniques like frequency division duplex (FDD) and code division multiple access (CDMA). To achieve higher rates of data transmission, 3x may make use of two 3.75 MHz channels, or multiple 1.25 MHz channels.

Since 3x is a multi-carrier version of Rev A, it is also sometimes referred to as "Multi-Carrier" or "MC." Its multi-carrier specification gives it a number of improvements over its predecessor. It has an increased maximum downlink rate of 14.7 Mbps (4.9 Mbps per carrier for 3 carriers is expected for typical transmission).

Expected peak rates for a 3x network with two channels are 6.2 Mbps for forward link throughput and 3.6 Mbps for reverse link throughput.

For one with three channels, expected peak rates are 9.3 Mbps for forward link throughput and 5.4 Mbps for reverse link throughput.

Interference from adjacent sectors was reduced and rate was improved by hybrid frequency re-use.

Latency was reduced by using statistical multiplexing across channels, enabling new services like video telephony, web browsing, gaming and remote console sessions.

Services such as high-definition video streaming were also enabled by bundling multiple channels together.

Talk time and standby time are also increased. 3x also provided ample support for services that required different data rates for uploading and downloading, such as delivery of broadband multimedia content, transferring of files, and web browsing.

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