What Are Hard Disk Bad Sectors?

If you are a regular computer user, chances are, you have encountered a message that says there are bad sectors in your hard disk. Your computer may allow you to boot and reach the desktop display but in some cases, you may not be able to boot your computer at all.

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What are hard disk bad sectors and why are these causing problems in your computer? An understanding of hard disk sector is required to clarify these issues.

Hard Disk Sector Defined

A sector is the basic unit of data storage on a magnetic platter, a metallic disk much like your compact disc, inside the hard drive (Figure 1). These sectors are arranged in a concentric manner relative to the center of the revolving disk. Taken together, the group of sectors make up a track. Of course you cannot see these things with your naked eye.

hard disk magnetic platter

Fig. 1. An opened hard disk showing the magnetic hard disk platter and the read/write head.

Each sector can hold a standard size of 512 bytes of data written by the disk head by transforming electrical signals into magnetic fields or do the opposite when reading. So the files you entered in your computer are stored in the many sectors of the hard disk drive along a track. These files, however, could not be accessed without an ID information. The ID information is a small space allocated to identify the sector’s number and location. This is used to locate the sector on the hard disk as well as provide for status information (if it’s good or bad) about the sector itself.

So what happens during those times you are alerted that your computer has bad sectors?

This simply means that the sectors where you record data are no longer accessible, hence are flagged by the hard disk as bad sectors. As data are written as a series of 1s and 0s, good sectors can be illustrated as 0011001010, while bad sectors are represented by 011?0?011?01. This means that data can no longer be read or written on that part of the hard disk.

Causes of Hard Disk Bad Sectors

Hard disk bad sectors normally occur in hard disk drives due to many reasons. Among the common ones are associated with the age of the hard disk drive, harsh operating conditions like high temperatures and vibration, overuse, among others.

Once your hard drive develops bad sectors, it is wise to save your data right away as long as you can still access some of your files. Your hard disk may be already old as hard drives normally last two years. If your files are no longer accessible or you can only access a part of it, you may try using softwares that can repair hard disk bad sectors. After disk repair, however, it is best to change your hard drive to avoid losing your precious data.

References

Dew Associates Corporation on Hard Disk Sector Structures

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Definition of Computer Networks and Its Advantages

Network is a anthology of computers associated to each other. It allows the computers to communicate with each other and sh resources which include information, software and peripheral devices such as printers, scanners

Now days, computers are used in a wider range. All the organizations are using multiple computers within their departments to perform their day to day work. It is necessary to connect them which form a network. The networks are classified into different types according to the network size. When computers communicate with each other, they follow certain specific formats and rules. This formats and rules are explained by the OSI (Open Systems Interconnection) model. This OSI model is conceptual and has seven layers and each layer is having its own functions.

 

As network selection criterion forms the basis of a network, since it helps to select a secured and efficient network. The criterion explains network performance improvement techniques and necessity of reliable network. Various standards organizations are used for network communication to maintain consistency.

Introduction to computer Networks

Computer network is an interconnection of two or more computers and peripherals such as printers and faxes. Computer network allows the user to share and transfer information using cables or modems within a network.

Need for Computer Networks

Computer network allows the user to share data with other users in a network, for example, a company having a number of computers which are connected in a network. Computer network will enable the users to share files and folders and get synchronized with other users.

Computer network also allows the user to share resources such as printers and faxes. Printer can be installed on one computer and can be accessed by other users in a network. By this the need of installing printers on individual computers is avoided and it results in cost-effectiveness. Computer network also allows the user to communicate with each other using instant messaging tools to share ideas, files or solve queries.

The user can also setup a central system wherein common files and folders which are frequently used by all the users can be stored. All the users within the network can easily access those files. Instead of taking backups from individual computer, the user can take data backup from the central system. This helps in reducing the time of taking backup.

If an organization you have several computers but just one phone line, a network makes it easier to use the Internet. Numerous computers can share one modem to use the equivalent Internet connection. Otherwise, you car even install a dedicated high-speed Internet connection such as a cable modem for your network.

It is possible to add new systems or servers to an existing network easily. Thus the computer network provides scalability. It is also reliable to use a network as it uses mirroring and redundancy

Source :  http://factoidz.com

Different Types of Ethernet Cables

Ethernet represents the cable (the ether) and the access protocol scheme. Cable is the intermediate through which data is transmitted from one network device to another. There are different types of cabling method used for Ethernet. The type of cable for a system is dependent on the network’s protocol, topology and size.
Different cabling standards for Ethernet include, 10Base5 (Thick coax), 10Base2 (Thin coax), 10Base-T (Twisted pair) and 10Base-F (Fiber optics). However, certain guidelines are to be followed before installing these cables.
• Length of the cable should be greater than the required length as per the design requirement
• Test every component after installation
• For laying cables across the floor, it is recommended to cover the cable with cable protectors
• Lay cable away from sources of electrical interference
• Use cable ties (not tape) to keep cables in the same location together. Label both ends of each cable
10Base-5
10Base-5 or Thick coaxial cable is also known as thicknet. 10Base5 means stipulation of thick coaxial cable transmitting Ethernet data. In 10Base 5, "5" means the utmost section measurement lengthwise being 500 mtrs. 10Base 5 employs thick RG-8 coaxial cable.
10Base-2
Coaxial cable consists of one physical route that transmits signal enclosed (after a layer of padding) by an additional concentric physical route, both operating alongside the same league. 10Base-2 or thin coaxial cable is also known as thinnet. 10Base2 means the stipulation for thin coaxial cable transmitting Ethernet signals.
10BASE-T
10BASE-T or Unshielded Twisted Pair is an execution of Ethernet which permits networks to be joined via twisted pair cable. In 10Base-T, means the communication speed of 10 Mbps. Base means baseband signaling, whereas "T" means twisted pair cable. Only one Ethernet signal is there on the send and/or receives pair.
10 Base-F (FOIRL- Fiber Optic Inter Repeater Link)
10 Base-F employs fiber optic cable, have outstanding noise opposition and is generally favored for cabling amid houses or extensively divided hubs. 10 Base-F is costly as the terminators and connectors used in 10 Base-F are expensive.

Source :  http://factoidz.com