Shulou(Shulou.com)06/03 Report--

This article mainly introduces "what is the structure of hard disk". In daily operation, I believe many people have doubts about the structure of hard disk. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubt about "what is the structure of hard disk?" Next, please follow the editor to study!

Content introduction

Why are we sorting out this note? In order to understand the composition of the hard disk. Understanding the disk structure helps us to understand the terms used in disk commands, such as fdisk (8), to understand how data is distributed on disks, to enhance our confidence in performing "high-pressure" disk operations, and to understand what actions occur during certain disk operations. Therefore, it is still necessary to understand the disk structure.

This note will introduce the disk structure and briefly introduce the disk composition structure (our focus is on the disk structure).

The physical composition of the disk

The PLATTER is a round metal disk, which is installed on the mainframe shaft inside the hard disk. Some hard drives contain multiple disks to provide more data storage in limited space.

The disk has a core made of aluminum (or glass) substrate and covered with a thin layer made of iron oxide or cobalt alloy. On both sides of the substrate, a very thin coating is deposited through special manufacturing technology. this thin coating is the place where the data is stored, called the dielectric layer. When the magnetic medium is applied to the surface of the substrate, it will be coated with a thin lubricated protective layer to protect the dielectric layer. This complex three-layer medium is as follows:

Substrate (underlayer material)

The substrate (underlying material) is used to form the shape of the disk and is also the place where the dielectric layer is deposited, except for no special purpose. Aluminum alloy is usually used as the substrate of the disk, which is very successful in the early days. With the progress of technology, the distance between the needle and the disc is shortened, and the rotating speed of the disc is higher, so new materials are needed to replace aluminum alloy. Glass discs are used to replace aluminum discs, which are more stable, of better quality and thinner.

Dielectric layer

The substrate is used to form the shape of the disk, and the dielectric layer is deposited on the substrate. It is a thin coating of magnetic material applied to the surface of the substrate, and it is also the place where the data are saved, and its thickness is only a few millionths of an inch.

The magnetic material is deposited on the substrate by "special technology". The substrate is coated with this thin coating on both sides, usually by vacuum evaporation called magnetron sputtering. Another method is electroplating, which is similar to the process used in electroplating accessories.

Note that both sides of the disk are coated with a media layer, which means that data can be stored on both sides of the disk. (note that this will affect our understanding of other content.)

Protective layer

The medium layer is coated with an ultra-thin, protective and lubricated protective layer. It is used to protect the disk from damage caused by accidental head contact, "head collision" and foreign body entering the disk.

The specific structure of the disk

In order to maintain organized discs and retrieve data, discs are organized into "specific structures". This "specific structure" is not the physical composition of the disk, but the logical partition method. These specific structures include orbits (Track), sectors (Sector), and clusters (Cluster).

Track (Track), magnetic column (Cylinder)

Each disc is divided into thousands of compact concentric circles, like tree rings, called orbits (Track). All the information saved on the disk is recorded in the track. The track value starts from zero at the outermost and moves to the innermost test. Each track can hold a large amount of data.

A track is a physical partition of data in a disk drive. The number of tracks on a single disc in the drive is exactly equal to the number of pillars in the drive.

How many tracks are there on a disk? It all depends on the manufacturer's layout of the hard drive.

How many tracks does a modern harddisk have?

Number of tracks

A magnetic column (Cylinder), which consists of tracks in "the same position" (the same track value) on multiple disks, is the smallest unit of disk partition.

Sector (Sector)

The track is divided into thousands of very small units called Sector. On the hard disk, the sector is the basic unit of data storage, and each sector can hold more than 512 bytes of data. A few additional bytes are used to control the structure and error checking.

Size: a traditional hard disk is a sector of 512 bytes, in CD-ROM it is 2048 bytes, and a newer hard disk uses a sector of 4096 bytes.

The composition of sectors: in modern disks, each physical sector consists of two parts:

1) the header, which contains the information used by the drive and controller.

2) data area, which is used to save data. We often say "the sector is 512 bytes", which only refers to the data area of the sector.

Cluster (Cluster)

On the hard disk, each partition is subdivided into Cluster. Clusters are the smallest possible units stored on a hard disk. Cluster size depends on two things: the size of the partition and the file system on the partition. The sectors are organized together to form clusters.

Other content capacity calculation

Therefore, the formula for calculating the capacity of "mechanical disk" is:

1) number of sectors * capacity of sectors * number of discs

2) number of disk read / write heads * number of columns per head * number of sectors per column * capacity

Each "Partition entry" is 16 bytes, its units are sectors, each sector 512 bytes, so the total number of bytes is: 512 x 2 ^ 16 x 8

In the PC XT era of hard disk technology products, partition tables use cylinders, heads, and sector (CHS addressing) units to subdivide storage media. These values no longer correspond to the names in modern disk drives and are independent of other devices, such as solid-state drives, which actually do not have cylinders or heads.

At this point, the study on "what is the structure of the hard disk" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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