How Do I Increase Hard Drive Memory?

Disk storage (magnetic disk storage), storage using magnetic disk as the storage medium. It is a secondary storage that uses magnetic recording technology to store data on a rotating disc coated with a magnetic recording medium. It has the characteristics of large storage capacity, high data transmission rate, and long-term storage of stored data.

In computer systems, disk memory is often used to store operating systems, programs, and data, and is an extension of main memory. The development trend is to increase storage capacity, increase data transmission rate, reduce access time, and strive to be light, thin, short and small. Disk storage usually consists of disks, disk drives (or disk drives), and disk controllers.

Chinese name: Disk storage
Foreign name: magnetic disk storage

Definition: Storage using disk as storage medium
Features: Large storage capacity and high data transfer rate

Disk storage structure principle

Disk storage is an auxiliary storage that uses magnetic recording technology to store data on a rotating disk medium. This is a widely used direct access memory. Its capacity is hundreds of times larger than the main memory. In computer systems of various sizes, it is often used to store operating systems, programs, and data. It is an expansion of the main memory. The data stored in the disk storage can be stored for a long time. Compared with other auxiliary storages, the disk storage has a larger storage capacity and a faster data transfer rate. A typical disk drive includes a disk spindle rotation mechanism and a drive motor, a head arm and a head arm bracket, a head arm drive motor, a cleaning disk cavity and an air purification mechanism, a write and read circuit, a servo positioning circuit, and a control logic circuit.

The disk rotates at a constant speed. The head block (floating magnetic head) with a floating surface suspended on the head arm is pressed against the disk surface by the force of a loaded spring, and the air flow driven by the disk surface floats the head block. Maintain a stable small gap between the head block and the disc. The air filtered by the dust filter is continuously sent into the disk cavity, keeping the disk and the head block in a highly purified environment to prevent the head block and the disk surface from being scratched. According to the track address (ie, the cylindrical address) and the seek command sent by the controller, the positioning circuit drives the linear motor to move the head arm to the target track. The servo head reads the servo track signal and feeds it back to the positioning circuit, so that the head arm follows the servo track to stabilize on the target track. The read-write and head-selection circuit turns on the selected head according to the head address sent by the controller, and records the data sent by the controller on the target track bit by bit in a serial manner; otherwise, it reads from the selected track The data is sent to the controller. The head arms are mounted on a comb cart, and all head arms move together during seek. Concentric circular tracks of the same diameter on all data planes are collectively referred to as cylindrical surfaces, that is, all the tracks that the head arm can access once it is positioned. Each track is recorded in a fixed format. After indexing the start position of the track, record the track's address (cylindrical surface number and top number), track status, and other reference information. At the end of each recorded segment is an error correction code for that segment. Errors caused by a few consecutive permanent defects are corrected by error correction codes. For tracks with multiple permanent defects, spare tracks must be used instead. Write and read operations are performed in units of record segments. There are two types of record segment length: fixed segment length and variable segment length.

Physical properties of disk storage

Magnetic disks are coated with planar discs on both sides of the magnetic disk. Data is recorded on magnetic media as closed concentric circular tracks.

Single-chip and multi-chip activity diagram This concentric circular track is called a track. The main technical parameters of a magnetic disk include the recording density, bit density, track density, and areal density. Bit density refers to how many bit units are recorded on a unit length on a concentric circular track of the disc, expressed in bits per millimeter (bpmm); track density refers to the number of tracks that can be accommodated per unit length in the radial direction of the recording surface, commonly used tracks / mm ( tpmm); area density refers to the bit unit recorded per unit area on the recording surface, and is usually expressed in bits / mm2. The storage capacity of a magnetic disk is the total number of binary digits that can be recorded on the disk. It is usually expressed in kilobytes (KB) or megabytes (MB). The access time includes the time required for the head to move from one track to another, the stabilization time after the head is moved, the disk rotation waiting time, and the head loading time is usually expressed in milliseconds (ms). Bit error rate refers to the ratio of the number of bit errors detected to the total number of bits in a batch of data after it is written to the device and read back.

Disk storage classification

A magnetic disk is a flat disc coated with a magnetizable medium on both sides. The data is recorded on the magnetic medium in a closed concentric circular track.

Disk storage This concentric circular track is called a track. Due to different disk bases, magnetic disks can be divided into hard disks and floppy disks. The hard disk base is made of non-magnetic light metal materials; the floppy disk base is made of flexible plastic. According to the installation method of the platter, there are two types of fixed and interchangeable (removable) disks. There are several interchangeable disk structures:

A component with a single disc mounted in a plastic or metal flat box is called a disc cartridge; a component with several discs coaxially connected together is called a disc group; a component with a magnetic disk and a magnetic head arm in a closed container is called a head disc Components. The platter of a small magnetic disk drive is directly mounted on the main shaft of the drive, and is integrated with the drive. A magnetic disk drive is a device that drives a magnetic disk to rotate and perform writing and reading operations on the disk surface. The disk pack or disk cartridge is mounted on the drive and rotates at a constant speed. The magnetic head floats on the surface of the disc. Under the control of the magnetic disk controller, data is written and read in concentric circular tracks on the magnetic surface of the disc through the magnetic conversion of the magnetic head. Disk drives are divided into two types: fixed head arm type and fixed head type; there are two types of removable head drive type: fixed type and fixed type.

Winchester disk storage is referred to as warm disk. It is named after Winchester technology. Winchester technology mainly includes: sealed head and disk assembly. That is, the magnetic head, the disk group and the positioning mechanism are sealed in a disk cavity. Later, it was developed that even the spindle motor and so on were all installed in the disk cavity, which can be replaced as a whole. The contact start-stop floating magnetic head with small size and small buoyancy is adopted. The result is an ultra-small head-to-disk gap (sub-micron order) to increase recording density. A thin-film magnetic recording medium with lubricating properties is used. Adopt magnetic fluid sealing technology. It can prevent dust, oil and gas from invading the disk cavity, thus keeping the disk cavity highly purified. Use a highly integrated preamplifier. Hard drives use Winchester technology. Compared with the replaceable magnetic disk, the recording density is greatly improved, the reliability of the magnetic disk drive is improved, and it is further miniaturized.

A floppy disk storage is referred to as a floppy disk, and is a recording medium that is enclosed in a square protective case and coated with a ferromagnetic layer on a soft substrate. The magnetic head and the disk surface of the floppy disk drive work in a contact state, so the rotation speed is very low, and other working principles are similar to those of the hard disk. Early floppy disks were 8 inches (1 inch = 2.54 cm) in diameter, but later developed into 5.25 inches, and 3.5-inch floppy disks were widely used. The thickness of the driver has also decreased year by year. Especially the thin 3.5-inch and 5.25-inch floppy disk machines have developed rapidly, and have been widely used in microcomputers and terminal equipment.

Disk storage

Fixed head arm disk storage or one head disk storage per lane. It does not require a head arm positioning mechanism, but instead installs as many head arms as possible for each panel. In order to reduce the average waiting time, the rotation speed of the disc is generally high, for example 6000 revolutions per minute. The performance characteristics of the fixed head arm disk and the magnetic drum are the same. Due to the expensive construction of the magnetic head, the application range is very small.

Disk memory drive control

Disk storage disk drive

A magnetic disk drive is a device that drives a magnetic disk to rotate and perform writing and reading operations on the disk surface by a magnetic head.

Disk drive schematic The disk is mounted on the drive and rotates at a constant speed. The magnetic head floats on the surface of the disc. Under the control of the disk controller, read and write data is performed on the magnetic layer of the disk surface through the electromagnetic conversion of the magnetic head.

Hard disk drives are divided into two types: fixed head arm type and fixed head arm type. The head arm mobile hard disk drive can be divided into interchangeable and fixed types. Because the new fixed disk uses Winchester technology, it is also called Winchester disk drive, referred to as Win Disk Drive.

The maximum number of data bits that a disk drive can transfer to a computer per second is called the data transfer rate, and it is expressed in kilobytes per second (KB / s) or megabytes per second (MB / s).

Disk storage disk controller

A disk controller is a disk drive adapter. It is the interface device between computer and disk drive.

Schematic diagram of the floppy disk structure It receives and interprets commands from the computer and sends various control signals to the disk drive. Check the status of the disk drive, write data to and read data from the disk in accordance with the specified disk data format. There are many types of disk controllers, but their basic composition and working principle are largely the same. It is mainly composed of a control logic circuit connected to the computer system bus, a microprocessor, a read and write data decoding and encoding circuit that completes the separation of read data and write data compensation, and a data error detection and correction circuit. A logic circuit that controls data transfer, serial-parallel conversion, and formatting. It consists of a read-only memory that stores basic I / O programs on the disk and a buffer for data exchange.

Disk storage technical indicators

The main indicators of disk storage include average latency, storage density, storage capacity, access time, data transfer rate, noise and temperature, etc.

Disk storage

Disk memory average latency

This indicator refers to how long it takes for the specified read / write sector to move below the magnetic head when the magnetic head moves to the specified track (the disk is rotating). The faster the disk rotates, the shorter the latency. The average latency is the time it takes the disk to make half a revolution. Obviously, the average latency of hard disks with the same speed is fixed. It is approximately 4.167ms at 7200RPM and 5.556ms at 5400RPM. ^[1]

Disk memory storage density

Storage density is divided into channel density, bit density and areal density. Track density is the number of tracks per unit length along the radius of the disk, and the unit is track / inch. Bit density is the number of bits of binary code that can be recorded per track length in units of bit / inch. Area density is the bit density and track density Product, in bits per square inch.

Disk memory storage capacity

The total number of bytes that a disk storage can store is called the storage capacity of the disk storage. The storage capacity is divided into formatted and unformatted capacity. Formatted capacity refers to the information that can be stored in accordance with a specific recording format. The total amount is the capacity that users can really use. The unformatted capacity is the total number of magnetized units available to the magnetic recording surface. When using disk storage in a computer system, it must be formatted before it can be recorded by users. The formatted capacity is generally 60% -70% of the unformatted capacity. The 3.5-inch hard drive has a capacity of 4.29GB.

Disk storage

Disk storage average access time

The access time is the time required for the head to move from a certain starting position to a new recording position after the read and write command is issued, and to start reading or writing information from the disc surface. This period of time is determined by two values Decision: one is the time required to position the magnetic head on the required track, called positioning time or seek time; the other is the time after the seek is completed and the information that needs to be accessed on the track reaches the head, called wait Time, both of which change randomly, so they are often expressed as averages. The average access time is equal to the sum of the average seek time and the average wait time. The average seek time is the average of the maximum seek time and the minimum seek time. The average seek time is 10-20ms. The average waiting time is related to the disk rotation speed. It is expressed by half of the time required for a disk to rotate for one week.

Disk memory data transfer rate

The number of bytes of data transferred from the disk storage to the host in a unit time is called the data transfer rate. The transfer rate is related to the storage device and host interface logic. Considering the host interface logic, there should be a fast enough transmission speed to receive / send information to the device. From the perspective of storage devices, assuming that the disk rotation speed is n revolutions per second and the capacity of each track is N bytes, the data transfer rate Dr = nN (bytes / second)

Floppy drive . It can also be written as Dr = D · v (bytes / second), where D is the bit density, v is the linear speed of the disk rotation, and the data transfer rate of the disk memory can reach tens of megabytes / second.

Disk storage noise and temperature

These two are non-performance indicators. For noise, manufacturers did not care about it before, but since 2000, due to market demand (such as OEM manufacturers want to produce quieter computers to increase selling points) manufacturers use various means to reduce the working noise of hard disks, ATA-5 The third edition of the specification also added Automatic Acoustic Management (AAM) subset, so all new hard disks support AAM function. The noise of the hard disk mainly comes from the spindle motor and voice coil motor, and noise reduction is also started from these two points (the increase of the disk will also increase the noise, but there is no way). As for the heat, each manufacturer has its own standard, and claims that the performance of the hard disk is what they expected, and it is completely within the safe range, no problem. Do nt worry about this, but the key is that the hard disk is an integral part of the chassis. Its high heat will increase the overall temperature of the chassis. Maybe the hard disk itself is fine, but the surrounding accessories may not be able to stand it. Two high-heat hard drives are installed closely together, so can they withstand nearly double the heat? So the heat of the hard disk still needs attention. ^[1]

A brief history of disk storage development

Disk storage first storage

The world's first hard disk storage was invented by IBM in 1956, and its model is: IBM350RAMA (RandomAccessMethodofAccountingandControl). The total capacity of this system is only 5MB, and a total of 50 disks with a diameter of 24 inches are used.

Micro hard disk

In 1968, IBM proposed the "Winchester / Winchester" technology, the main point of which was to seal the high-speed rotating magnetic disks, magnetic heads, and its seek mechanism in a dust-free enclosure to form a head-disk assembly ( HDA), which is isolated from the external environment, avoids dust pollution, and uses miniaturized light buoyancy magnetic head sliders, the surface of the disc is coated with lubricant, and the contact is started and stopped. This is the prototype of most modern hard drives.

In 1979, IBM invented the thin-film magnetic head, which further reduced the weight of the magnetic head, enabling faster access speeds and higher storage density.

The emergence of disk storage micro hard disk

In the late 1980s, IBM made another significant contribution to disk technology and invented the MR (MagnetoResistive) magnetic head, which is very sensitive to changes in the signal arrangement directory when reading data, making the storage density of the disc It has increased by dozens of times compared with the past. In 1991, the 3.5-inch hard disk produced by IBM used MR magnetic heads to increase the capacity of the hard disk to 1 GB for the first time. Since then, the hard disk capacity has entered the order of GB. IBM also invented the PRML (PartialResponseMaximumLikelihood) signal reading technology, which greatly improves the sensitivity of signal detection, which can greatly increase the recording density.

At the beginning of the 21st century, the areal density of hard disks has reached more than 100Gb per square inch, making it the storage device with the highest capacity and cost performance. Therefore, among the external storage devices of computers, no other storage device can challenge its dominance. Hard disk is not only used in various computers and servers, it is also a basic storage unit in disk arrays and various network storage systems.

It is worth noting that with the emergence and rapid development of micro hard disks, an ideal storage medium has been provided for mobile storage. In the field of large-capacity mobile storage, which is difficult for flash memory chips, micro-hard disks can play an important role. The 1-inch hard drive has a storage capacity of 8GB, and a 1-inch hard drive with a 20GB capacity will soon be available.