What Are Hard Disk Bad Sectors?
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What Are Hard Disk Bad Sectors?

Computers have hard disks that tend to develop bad sectors over time with constant use. The presence of bad sectors can prevent one from using the computer thus access files that have been saved in the hard disk. But what is a bad sector and what are the probable causes of its occurrence? This article explains this commonly used computer jargon to aid computer users in understanding how their hard disk works thus effectively address problems associated with it.

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 and access your files but in some cases, you may not be able to boot your computer at all.

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 and will no longer be read by the disk head. 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 with the question mark. The series of ones and zeroes are binary codes that represent symbols, letters or instructions.

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.


Dew Associates Corporation on Hard Disk Sector Structures

Data Clinic

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Comments (8)

Voted you up.Well written, informative article.

very informative

I do not believe that I have ever read such a simple but adequate explanation of sectors or bad sectors before. Even someone who is computer illiterate should be able to understand this material. Really good work, Patrick.

Thanks for information. Excellent article. Voted up.

I often encounter this. Thanks for sharing.

Thank you for this alert. I will be aware should I ever encounter it. I wanted to read this, however do not have a vote now. I will return later when I have one for you since this is a valuable article worthy of a vote.

Didn't know about this so thanks for the information.

All I know before is about hard disk, thanks for providing this great content. Now, I understood about hard disk drives. Thank you for sharing this informative article, voted and shared.