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Thursday, March 26, 2009

What is Storage Area Network

What is Storage Area Network

Knowing your computer is very vital sometimes it is not enough to only use tools like anti-spyware, anti-virus, registry cleaner etc. to fix some problems. This article lets you know what storage area network is.

SAN is a dedicated network that is separate from LANs and WANs. It is generally used to connect all the storage resources connected to various servers. It consists of a collection of SAN Hardware and SAN software; the hardware typically has high inter-connection rates between the various storage devices and the software manages, monitors and configures the SAN.

A storage area network is a high-speed special-purpose network that interconnects different kinds of data storage devices with associated data servers on behalf of a larger network of users. In computing, a storage area network is an architecture to attach remote computer storage devices such as disk arrays, tape libraries and optical jukeboxes)to servers in such a way that, to the operating system, the devices appear as locally attached. SANs are still uncommon outside larger enterprises.

By contrast to a SAN, network-attached storage uses file-based protocols such as NFS or SMB/CIFS where it is clear that the storage is remote, and computers request a portion of an abstract file rather than a disk block.

San Infracture

A SAN's architecture works in a way that makes all storage devices available to all servers on a LAN or WAN. As more storage devices are added to a SAN, they too will be accessible from any server in the larger network. In this case, the server merely acts as a pathway between the end user and the stored data.

Because stored data does not reside directly on any of a network's servers, server power is utilized for business applications, and network capacity is released to the end user.

A storage area network can use existing communication technology such as IBM's optical fiber ESCON or it may use the newer Fiber Channel technology. Some SAN system integrators liken it to the common storage bus 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 system.

A SAN is made up of a number of fabric switches connected in a network. The most common form of SAN uses the Fiber Channel fabric protocol with Fiber Channel switches. Alternatively ISCSI could be used with IP switches.

Connected to the SAN will be one or more Disk array controllers and one or more servers. The SAN allows the storage space on the hard disks in the Disk array controllers to be shared amongst the servers.




Storage Area Types

Most storage networks use the SCSI protocol for communication between servers and disk drive devices. However, they do not use SCSI low-level physical interface as its bus topology is unsuitable for networking. To form a network, a mapping layer is used to other low-level protocols:

iFCP or SANoIP, mapping SCSI over Fibre Channel Protocol over IP.
iSCSI, mapping SCSI over TCP/IP.
iSER, mapping iSCSI over InfiniBand
HyperSCSI, mapping SCSI over Ethernet.
FICON mapping over Fiber Channel used by mainframe computers.
ATA over Ethernet, mapping ATA over Ethernet.
Fiber Channel over Ethernet

What is SPAM Email

What is SPAM Email

E-mail spamming, also known as "bulk e-mail" or "junk e-mail," is a subset of spam that involves nearly identical messages sent to numerous recipients by e-mail. A common synonym for spam is unsolicited bulk e-mail (UBE). Definitions of spam usually include the aspects that email is unsolicited and sent in bulk "UCE" refers specifically to "unsolicited commercial e-mail."

E-mail spam has existed since the beginning of the Internet, and has grown to about 90 billion messages a day, although about 80% is sent by fewer than 200 spammers. Botnets, virus infected computers, account for about 80% of spam. Laws against spam have been sporadically implemented, with some being opt-out laws and others being opt-in. The total amount of spam has leveled off slightly in recent years. The cost of spam is borne mostly by the recipient, so it is a form of postage due advertising.

E-mail addresses are collected from chat rooms, websites, newsgroups, and viruses which harvest users address books, and are sold to other spammers. Much of the traffic is sent to invalid e-mail addresses. ISPs have attempted to recover the cost of spam through lawsuits against spammers, although they have been mostly unsuccessful in collecting damages despite winning in court.

Types Of Spam

Spam has several definitions, varying by the source.

• Unsolicited bulk e-mail (UBE)—unsolicited e-mail, sent in large quantities.

• Unsolicited commercial e-mail (UCE)—this more restrictive definition is used by regulators whose mandate is to regulate commerce, such as the U.S. Federal Trade Commission.

• Any email message that is fraudulent.

• Any email message where the sender’s identity is forged, or messages sent though unprotected SMTP servers, unauthorized proxies, or botnets

Anti-spam techniques

Some popular methods for filtering and refusing spam include e-mail filtering based on the content of the e-mail, DNS-based blackhole lists (DNSBL), greylisting, spamtraps, Enforcing technical requirements of e-mail (SMTP), checksumming systems to detect bulk email, and by putting some sort of cost on the sender via a Proof-of-work system or a micropayment. Some of the registry cleaner tools even give you spam monitors in a package when you buy from them. Each method has strengths and weaknesses and each is controversial due to its weaknesses.

Detecting spam based on the content of the e-mail, either by detecting keywords such as "viagra" or by statistical means, is very popular. Such methods can be very accurate when they are correctly tuned to the types of legitimate email that an individual gets, but they can also make mistakes such as detecting the keyword "cialis" in the word "specialist". The content also doesn't determine whether the email was either unsolicited or bulk, the two key features of spam. So, if a friend sends you a joke that mentions "viagra", content filters can easily mark it as being spam even though it is neither unsolicited nor sent in bulk.
The most popular DNSBLs are lists of IP addresses of known spammers, open relays, zombie spammers etc.

Spamtraps are often email addresses that were never valid or have been invalid for a long time that are used to collect spam. An effective spamtrap is not announced and is only found by dictionary attacks or by pulling addresses off hidden webpages. For a spamtrap to remain effective the address must never be given to anyone. Some black lists, such as spamcop, use spamtraps to catch spammers and blacklist them.

Enforcing technical requirements of the Simple Mail Transfer Protocol (SMTP) can be used to block mail coming from systems that are not compliant with the RFC standards. A lot of spammers use poorly written software or are unable to comply with the standards because they do not have legitimate control of the computer sending spam (zombie computer).

So by setting restrictions on the mail transfer agent (MTA) a mail administrator can reduce spam significantly. In many situations, simply requiring a valid fully qualified domain name (FQDN) in the SMTP's EHLO (extended hello) statement is enough to block 25% of incoming spam.

Similarly, enforcing the correct fall back of Mail eXchange (MX) records in the Domain Name System, or the correct handling of delays (Teergrube) can be effective.

How Instant Messaging Work

How Instant Messaging Work

There are several ways you can talk to people in person, on the phone, via e-mail, and instant messaging. There are several programs that come with an instant messenger capability. You have the two most popular Yahoo instant messenger and aim messenger, which is AOL's instant messenger. MSN also has an instant messaging program. There is also a program that is called ICQ.

These are all great instant messengers you can use. What is instant messenger? Well it's not a registry cleaner but really dang cool - it's basically like sending a text message to a person on a cell phone. And we all know people who love to text on phones. So instant messaging is a way to talk to your friends, relatives, strangers, bosses or whoever you might want to talk to. Most instant messengers have ways for you to look for friends who have similar interests, live in certain areas, like the same movies as you, or several other things. This is one good way to look for new friends. You can talk to people from other countries. Instant messaging can keep you busy for hours just chatting with friends. It's also a cool way to keep up with relatives instead of running up astronomical phone bills.

Plus with instant messaging, you can also share pictures with people, and sometimes funny videos. Instant messaging is really a cool thing, so flex those fingers and get to typing.

Instant messaging with friends and relatives is as close to talking on the phone. But it's nicer because at times when you're tired of talking, you may be able to beg off on the computer easier than on the phone. In fact, a few times with friends who have become long winded and I've been saying I'm tired and they just keep going on and on. I've actually shut down the instant messenger program, next time I get on I just tell them that I got kicked off the computer. This happens to so many people that they won’t even question whether or not it actually happened.

It may not be the nicest thing to do, but at times you just are done with writing. Or another trick to use is to sign in invisible, this way no one can tell you're there, but you can see who comes online. I do this almost all the time when I'm working. This way I can avoid the interruptions.

What is the Importance of Internet Security

What is the Importance of Internet Security

In the computer industry, Internet security refers to techniques for ensuring that data stored in a computer cannot be read or compromised by any individuals without authorization. Most security measures involve data encryption and passwords. Data encryption is the translation of data into a form that is unintelligible without a deciphering mechanism. A password is a secret word or phrase that gives a user access to a particular program or system.

Internet security can be achieved through following steps.

Internet service provider

Your Internet service provider (ISP) should be your first line of defense. If you have a choice, choose an ISP that offers online virus, spam and content filters. This will reduce, but not eliminate, the amount of spam and the number of infected emails that you receive. The content filter is to protect your kids. If you do not have a choice or want to keep your current ISP, consider using an online email service that offers virus and spam filters. For more information, see our Broadband page.

A variety of Privacy Software is available to clean your browser, stop spam, trip up phishing, filter content for kids, catch web bugs, manage cookies, and block banner, pop-up and pop-under ads. These are routers, firewalls, anti-virus, anti-spyware and registry cleaner. For more information, see our Privacy, Anti-Spam and Anti-Phishing pages.

Routers

Routers provide the security from internet using Network Address Translation technique. Network Address Translation (NAT) typically has the effect of preventing connections from being established inbound into a computer, whilst permitting connections out. For a small home network, software NAT can be used on the computer with the Internet connection, providing similar behavior to a router and similar levels of security, but for a lower cost and lower complexity.

Firewalls

A firewall blocks all "roads and cars" through authorized ports on your computer, thus restricting unfettered access. A stateful firewall is a more secure form of firewall, and system administrators often combine a proxy firewall with a packet-filtering firewall to create a highly secure system. Most home users use a software firewall. These types of firewalls can create a log file where it records all the connection details (including connection attempts) with the PC.

Anti-virus

Some people or companies with malicious intentions write programs like computer viruses, worms, Trojan horses and Spyware. These programs are all characterized as being unwanted software that installs automatically on your computer through deception.

Trojan horses are simply programs that conceal their true purpose or include a hidden functionality that a user would not want.

Worms are characterized by having the ability to replicate themselves and viruses are similar except that they achieve this by adding their code onto third party software. Once a virus or worm has infected a computer, it would typically infect other programs (in the case of viruses) and other computers.

Viruses also slow down system performance and cause strange system behavior and in many cases do serious harm to computers, either as deliberate, malicious damage or as unintentional side effects.

In order to prevent damage by viruses and worms, users typically install antivirus software, which runs in the background on the computer, detecting any suspicious software and preventing it from running.

Some malware that can be classified as Trojans with a limited payload are not detected by most antivirus software and may require the use of other software designed to detect other classes of malware, including Spyware.

Anti-Spyware

Spyware is software that runs on a computer without the explicit permission of its user. It often gathers private information from a user's computer and sends this data over the Internet back to the software manufacturer.
Adware is software that runs on a computer without the owner's consent, much like Spyware. However, instead of taking information, it typically runs in the background and displays random or targeted pop-up advertisements. In many cases, this slows the computer down and may also cause software conflicts.

How Search Engine on the Web Works

How Search Engine on the Web Works

Web Search Engine is a search engine designed to search for information on the WWW. Information may consist of web pages, images and other types of files.

Some search engines also mine data available in newsgroups, databases, or open directories. Unlike Web directories, which are maintained by human editors, search engines operate algorithmically or are a mixture of algorithmic and human input.

The very first tool used for searching on the Internet was Archie.The name stands for "archive" without the "vee". It was created in 1990 by Alan Emtage, a student at McGill University in Montreal. The program downloaded the directory listings of all the files located on public anonymous FTP (File Transfer Protocol) sites, creating a searchable database of file names; however, Archie did not index the contents of these files.

The first Web search engine was Wandex, a now-defunct index collected by the World Wide Web Wanderer, a web crawler developed by Matthew Gray at MIT in 1993.

How they work

A search engine operates, in the following order:

Web crawling
Indexing
Searching

Web search engines work by storing information about many web pages, which they retrieve from the WWW itself. These pages are retrieved by a Web crawler an automated Web browser which follows every link it sees. Exclusions can be made by the use of robots.txt. The contents of each page are then analyzed to determine how it should be indexed. Data about web pages are stored in an index database for use in later queries.

Some search engines, such as Google, store all or part of the source page as well as information about the web pages, whereas others, such as AltaVista, store every word of every page they find. This cached page always holds the actual search text since it is the one that was actually indexed, so it can be very useful when the content of the current page has been updated and the search terms are no longer in it.

This problem might be considered to be a mild form of linkrot, and Google's handling of it increases usability by satisfying user expectations that the search terms will be on the returned webpage. This satisfies the principle of least astonishment since the user normally expects the search terms to be on the returned pages.

Increased search relevance makes these cached pages very useful, even beyond the fact that they may contain data that may no longer be available elsewhere.

When a user enters a query, e.g. registry cleaner, into a search the engine examines its index and provides a listing of best-matching web pages according to its criteria, usually with a short summary containing the document's title and sometimes parts of the text. Most search engines support the use of the boolean operators AND, OR and NOT to further specify the search query. Some search engines provide an advanced feature called proximity search which allows users to define the distance between keywords.

Geospatially-enabled Web search engines

A recent enhancement to search engine technology is the addition of geocoding and geoparsing to the processing of the ingested documents being indexed, to enable searching within a specified locality or region. Geoparsing attempts to match any found references to locations and places to a geospatial frame of reference, such as a street address, gazetteer locations, or to an area. Through this geoparsing process, latitudes and longitudes are assigned to the found places, and these latitudes and longitudes are indexed for later spatial query and retrieval. This can enhance the search process tremendously by allowing a user to search for documents within a given map extent, or conversely, plot the location of documents matching a given keyword to analyze incidence and clustering, or any combination of the two. See the list of search engines for examples of companies which offer this feature.

How To Download And Install Computer Programs

How To Download And Install Computer Programs

Computer Programs are important for the user to communicate with the computer. Users need to install computer programs to make sure that the computer will work the way users need to. There are also computer programs or softwares that you can download from internet websites to help you in more specific and advanced tasks.

Many computer programmers create computer programs or improve existing computer programs for users to purchase and download from the internet.

However, because of the proliferation of computer viruses that may harm the computer like deleting files, or crashing the system, users need to be careful in downloading and installing computer programs.

It is therefore necessary that before you download or install a computer program into your computer, you will be able to assess if the program is going to harm your computer or not.

It is often difficult to assess the possibility of a computer program damaging your computer by mere description or advertisement provided by the computer programmer or program manufacturer. It is necessary that you analyze the computer program before embarking on purchasing or downloading such computer program.

Things to consider before downloading or installing computer programs

Know what the computer can do for you and what it can do to your computer. Ask the manufacturer for information and detailed description of the computer program. The manufacturer may post this in its website or provide you with copy of a manual. You will need to know what other things the computer program can do to your computer other than the function that the manufacturer tells you or advertised it can do.

Check for reviews. The written description or information of the computer program may not be enough for you to assess the computer program properly. Thus, you will need to look for other individuals who might have used or tried the computer program. Reviews posted on the internet may help you understand the program better and this is something that you need to look for before you download and install a new computer program.

Know the company or individuals who created or designed the computer program. The computer program manufacturer should be accessible to the user. Ask for their email address, telephone number, address and the registered manufacturer of the computer program. You may check the company with the Better Business Bureau to know if they are legally operating as computer program manufacturer. You may also try contacting them through telephone or email. If the manufacturer is legitimate, you will easily get in touch with them and thus, when problems arise, you are sure you can reach the people responsible for the computer program.

Backup important files in your computer. Because you will be installing a new computer program. You will avoid the risk of loosing important files by doing a backup in a CD or USB. This is to make sure that should anything untoward happen; you will be able to retrieve your important files.

If the computer program is able to pass the rigid analysis above, download and install the computer program after you have ensured that your anti-virus program and registry cleaner is working properly.

You may have analyzed the new computer program but then being able to doubly protect your computer with anti-virus program is always necessary