What is a Sector?

A sector is an equal sized division of hard drive, optical disc, floppy disk, thumb drive or any other storage media. A sector, disk sector or a block are the same things.

What is a Sector?

What is a Sector

What do Different Sector Sizes Mean?

Every sector resides on a physical location on the drive and consists of three parts: sector head, error-correcting mode (ECC), and the area to store the data.

A sector of hard drive or floppy disk can store about 512 bytes of information and this standard was announced in 1956. Then, in the 1970s its size increases to 1024 and 2048 bytes for larger storage capacities. Optical disk sector stores around 2048 bytes.

In 2007, a sector was announced of 4096 bytes for Advanced Format hard drives and then in 2011, it became standard for modern hard drives.

The size of the sector only increases or decreases the number of sectors in a hard drive to determine capacity and has nothing to do with sizes of hard drives or optical drives.

Disk Sectors and Allocation Unit Size

While formatting a hard drive you can clearly define the custom allocation unit size (AUS). This defines the smallest portion of the disk which can store data.

If we talk about Windows you have complete freedom to choose format what you like in the following sizes: 512, 1024, 2048, 4096, or 8192 bytes, or 16, 32, or 64 kilobytes.

For instance, you have a 1 MB (1,000,000 bytes) document file. Either you store this file on the floppy disk having 512 bytes in each sector or on the hard disk drive having 4096 bytes per sector. Regardless of the size of the sector, it matters how large the entire device is.

The real difference between the device having 512 bytes sector and other having 4096 bytes per sector is that the 1 MB file will be spanned across more disk sectors than of 4096 bytes per sector device. As 512 is smaller than 4096 that means fewer pieces of the file will be able to exist in each sector.

In this example, if the file size is increased to 5 MB, which is the increment of 4 MB. If the file is stored on the 512-byte drive. The pieces of the file will be stored in different sectors which can be at any place on the hard drive and this process is called fragmentation.

Whereas, if the file is stored on a 4096-byte allocation unit size, the 4 MB of data will take much less space due to the large size of the sector and the cluster of the sector will be close decreasing the fragmentation process.

Generally, the larger AUS is the more close file will be an easy and quick to access which impacts the overall computer performance.

Changing the AUS

You can check the cluster size in your hard drive if you running Windows or any other Operating System. You can use fsutil command for that. For instance, you can use the command-line tool and enter the command fsutil fsinfo ntfsinfo c: and you will get the cluster size of C: drive.

Though it’s not performed commonly, you can check the default cluster size table for NTFS, FAT, and exFAT file system for different versions of Windows. For instance, the default AUS is 4 KB (4096 bytes) for most of the hard drives which are mostly formatted using the NTFS system.

But if you want to change the cluster size, either do it from Windows when you are formatting your hard disk, but you can also use third party tool to deal with it from disk management.

You should use built-in Windows tool for formatting or there are several free programs to do this.

Repairing Bad Sectors

When a hard drive is damaged that’s basically the sectors physically damaged on the platter of the drive but it can also be damaged by corruption or another type of damages.

The most frustrating sector is the boot sector. If this sector creates a problem the whole OS is unable to boot.

Hard drive’s sectors can be damaged and can be repaired using a software program. These programs can correct, identify or mask-as-bad, disk sectors. In case there are several bad sectors, it’s recommended to change your hard drive.

But sectors cannot be responsible for other issues in your computer for example if the hard drive is making noise or your computer is getting slow. Troubleshooting or scanning can further tell you about it.

More Information on Disk Sectors

The sectors located near the center are weak compared to the sectors located near the external ends. So there’s something called zone bit recording.

Zone bit recording divides the disk into several zones and each zone is further divided into sectors. The outer portion gets more sectors allowing the hard drive to access quickly compared to zones located near the center.

Defragmentation tools take advantage of the zone bit recording to move commonly accessed file in outer portions for quick access. The data you access less often is moved to the center and that’s why it can take longer to access.

What Is Fragmentation & Defragmentation?
NTFS File System