Computer Fundamentals 简明教程

Actuator − The actuator arm is a mechanical element responsible for providing support to the read/write heads. The mechanism facilitates the movement of the read/write heads to the intended track on the platter for the purpose of data reading or writing. Contemporary hard disc drives (HDDs) employ voice coil actuators to achieve precise positioning.

Read-write Heads − Every platter is equipped with a corresponding read/write head that hovers slightly above its surface. These components are tasked with the responsibility of retrieving data from and storing data onto the platters. The actuator arm is utilised to swiftly traverse the surface of the platter, facilitating access to various sections of the disc.

Central Spindle − Platters rotate at a consistent pace with the spindle. Most HDDs spin at 5,400 or 7,200 RPM, while some high-performance devices spin at 10,000 or 15,000 RPM.

Magnetic Platter − it stores information in binary form. The flat, round discs inside an HDD are called platters. Most of the time, these plates are made of aluminium or glass and have a magnetic coating. Magnetic patterns keep the information on the platters.

Power Connectors − It links hard drive to circuit board in personal computer. A power connector is needed to power internal HDDs from the computer’s power source. Modern discs use SATA power connectors.

Read-Write Head − is a tiny magnet on the end of the read-write arm.

Circuit Board − The controller board, also called a "Printed Circuit Board" (PCB), is the HDD’s brain. It holds the drive’s software, which controls how data is accessed and fixes errors. The drive is also connected to the computer’s interface (such as SATA or IDE) by the driver board.

Data Connector − The computer’s power supply device powers internal HDDs through a power connector. SATA power connectors are common for newer drives.

Small Spindle − This allows read-write arm to swing across platter.

Data Storage − HDDs consist of one or more rigid, rapidly rotating disks (platters) coated with a magnetic material. Data is stored on these platters in the form of magnetic patterns. To read or write data, a read/write head moves over the spinning platters.

Capacity − HDDs are available in various storage capacities, ranging from a few gigabytes (GB) to multiple terabytes (TB). The capacity of an HDD is determined by the number of platters it contains and their data density.

Speed − HDDs are generally slower than SSDs in terms of data access times and read/write speeds. This is because the read/write heads need to physically move to the correct location on the disk, causing latency.

Durability − HDDs are mechanical devices with moving parts, which makes them susceptible to mechanical failure if subjected to physical shocks, drops, or excessive vibration. SSDs, being solid-state, are more durable in this regard.

Price − HDDs are typically less expensive per gigabyte compared to SSDs. This makes them a cost-effective choice for large storage needs.

Noise and Heat − HDDs can generate noise due to the spinning platters and moving heads. They also generate heat, so proper ventilation is necessary to prevent overheating.

Power Consumption − HDDs generally consume more power than SSDs because of the mechanical components. This can lead to slightly higher electricity usage in laptops and desktops.

Longevity − The lifespan of an HDD can vary but is often shorter than that of an SSD. Over time, the mechanical parts can wear out, leading to data loss.

Applications − HDDs are commonly used for various purposes, such as storing large files (photos, videos, and documents), running operating systems and software, and in network-attached storage (NAS) devices for backup and data sharing.

Backup − Due to their mechanical nature, it’s important to regularly back up data on HDDs to prevent loss in case of failure. Redundant storage systems or RAID configurations can be used for added data protection.

Magnetic Platters − Platters refer to circular plates. The number of platters in a hard drive is directly proportional to its storage capacity, as each platter can accommodate a specific quantity of information. Consequently, a hard drive with greater storage capacity would include a larger number of platters compared to one with lesser storage capacity. The process of storing and retrieving information from the platters involves the utilisation of concentric circles known as tracks, which are further divided into sectors.

Arm − The arm refers to the component protruding above the platters. The arms equipped with read and write heads that are utilised for the purpose of reading and storing magnetic data onto the platters. Each platter will possess an own arm that is utilised for the purpose of reading and writing data from and onto it. The motor is employed to rotate the discs at speeds ranging from 4,500 to 15,000 revolutions per minute (RPM). A higher rotational speed of a drive corresponds to improved performance outcomes. When a computer requires data retrieval from the hard drive, the motor initiates the rotation of the platters, while the arm repositions itself to the designated location above the platter where the data is stored. The magnetic heads located on the arm are responsible for detecting the magnetic bits present on the platters. These heads then convert the detected bits into the corresponding data, which can be utilised by the computer. In contrast, during the process of data transmission to the drive, the magnetic heads will emit magnetic pulses towards the platters, so altering the magnetic characteristics of the platter surface and subsequently storing the information.

NAND Flash Memory − The primary component of an SSD is NAND flash memory. This is a type of non-volatile storage that retains data even when the power is turned off. NAND flash memory is made up of memory cells organized into pages and blocks.

Cells and Bits − Each memory cell in NAND flash can store multiple bits of data, typically one, two, or three bits per cell. The more bits a cell can store, the more cost-effective the SSD is, but it can also affect performance and longevity.

Pages and Blocks − Data is written and read from NAND flash memory in fixed-size pages, which are grouped into larger blocks. When data is written to an SSD, it is first programmed into an empty page. To update or delete data, SSDs use a process called wear-leveling, which ensures that data is evenly distributed across the NAND cells to prevent excessive wear on any one cell.

Controller − The SSD controller is a critical component that manages the reading and writing of data to and from the NAND flash memory. It handles tasks such as error correction, wear leveling, and garbage collection to optimize performance and longevity.

TRIM − The TRIM command is an important feature of SSDs. It allows the operating system to inform the SSD which data blocks are no longer in use, allowing the SSD to perform efficient garbage collection and wear leveling, which helps maintain performance over time.

Wear Leveling − NAND flash memory cells have a limited number of write-erase cycles before they degrade. Wear leveling ensures that data is written evenly across the memory cells, extending the lifespan of the SSD.

Read and Write Operations − SSDs can read data very quickly since there are no moving parts involved. Write operations, however, can be more complex because data must be written to empty pages and previously used pages must be erased before they can be rewritten. This process is managed by the SSD controller to optimize speed and minimize write amplification.

Recording Mechanism − Magnetic tape is a long, thin plastic strip covered with magnets. Magnetising regions representing binary 0s and 1s stores data on tape.

Reading Mechanism − As tape runs through a tape drive, magnetised portions are read to recover data. This sequential procedure requires the drive to fast forward or rewind to access specific data, which is slower than random access storage like hard drives or SSDs.

CD (Compact Disc) − CDs were one of the earliest types of optical discs and were released in the early 1980s. They can store up to 700 MB of data and are widely used for music, software, and data storage.

DVD (Digital Versatile Disc) − After CDs, DVDs have substantially higher storage capacity, 4.7 GB single-layer and 8.5 GB dual-layers. In movies, software distribution, and data backup.

Blu-ray Disc − Newer optical discs like Blu-rays can store more data than DVDs. They can hold 25 GB (single-layer) and 50 GB (dual-layer) for standard discs and more for specialised versions. Blu-ray discs are utilised for HD video and data storage.

Archival Disc − Archival optical discs preserve data for long periods. Archival-grade data volume and durability make them ideal.

Recordable and Rewritable Discs − Rewritable and write-once optical discs are available. Rewritable discs can be erased and rewritten, however recordable discs can only be written once.

Recording Mechanism − Lasers create tiny pits and lands on CDs, DVDs, and Blu-rays. Pits and lands are binary data.

Reading Mechanism − The disc drive’s laser detects pits and lands' reflections to read data. Drive converts reflections into digital data.

Storage Capacity − USB flash drives are available in a wide range of storage capacities, spanning from a few gigabytes (GB) to several terabytes (TB).

Physical Size − These devices are generally characterised by their small and compact size, resembling a plastic or metal stick with a USB connector located at one end. These devices are specifically engineered for convenient portability, allowing them to be effortlessly carried in a pocket or securely attached to a keychain.

Data Transfer Speed − USB flash drives exhibit varying data transfer speeds, typically classified according to USB generations, including USB 2.0, USB 3.0, USB 3.1, and USB 3.2. Every successive generation presents enhanced data transfer rates. USB 3.0 and subsequent iterations exhibit notable enhancements in speed compared to USB 2.0.

File Storage − A USB flash drive is capable of storing a wide range of data types, including documents, photos, videos, music, software, and other files. These devices are frequently utilised for the purpose of transferring files between various devices or serving as a reliable backup storage solution.

Plug-and-Play − USB flash drives are commonly recognised as plug-and-play devices, which implies that they can be effortlessly connected to a USB port on a computer and are immediately operational, without necessitating the installation of supplementary drivers or software.

Security − Certain USB flash drives are equipped with integrated security features, including hardware encryption and password protection, which serve to enhance the protection of your data in the event of loss or theft of the drive.

Price − The pricing of USB flash drives is subject to variation depending on factors such as storage capacity, speed, and brand. In general, drives with smaller capacities are typically more cost-effective, whereas drives with larger capacities and faster speeds tend to be priced at a higher range.

Secure Digital (SD) Card − SD cards are popular memory cards. MicroSD, miniSD, and normal SD are available. Digital cameras, smartphones, and other portable devices require SD cards.

CompactFlash (CF) Card − SD cards are smaller and weaker than CompactFlash cards. Professional cameras and industrial applications use them.

Memory Stick − Memory Stick cards were popular in Sony cameras, camcorders, and laptops.

XQD and CFexpress − These high-speed memory card formats are utilised in professional cameras and video recorders. They can capture high-resolution photos and videos due to their quick read and write rates.

MultiMediaCard (MMC) − MMC cards are smaller than SD cards and used in older devices. Today they’re uncommon.

SmartMedia Card − Most digital cameras and other portable devices no longer use SmartMedia cards.

Network Attached Storage (NAS) − NAS hard drives are designed for household and small business file sharing and storage. Multiple storage bays, RAID functionality, and built-in network connectivity make file access and sharing easy.

Storage Area Network (SAN) − Multiple servers receive block-level storage from high-performance. SAN’s using specialised hard drive systems. Data centres and enterprises utilise them to centralise and manage storage resources.

Video Surveillance Storage − Video surveillance systems need hard drives for continuous HD video recording and playback. These drives are optimised for write-intensive workloads and surveillance.

Gaming Storage − Some consoles and high-end PCs include specialised hard drives for fast loading and smooth gaming. SSDs minimise load times on these discs.

Ruggedized Hard Drives − Durable hard drives can survive extreme temperatures, stress, and vibration. Industries like military, aerospace, and industrial automation employ them.

Data Recovery Systems − To recover data from damaged or corrupted drives, data recovery businesses utilise specialised hard drive systems with modern tools and software.

Medical Imaging Storage − Medical imaging technologies like MRI and CT scans create massive amounts of data that hospitals need to store. Specialised storage solutions protect data and comply with privacy laws.

Digital Content Creation (DCC) Storage − DCC professionals like video editors and 3D animators need high-capacity, high-speed storage for huge multimedia files. These needs are met by specialised storage systems.

Scientific Research Storage − Scientific research, notably genomics and particle physics, requires huge data storage and analysis. Effective big data jobs require specialised storage solutions.

Media Types − Magnetic tapes, optical discs, and archival media are used in tertiary storage systems. These inexpensive media can hold lots of data.

Low Access Speed − Tertiary storage accesses data slower than primary and secondary storage. To read tape data, you must physically move it.

High Capacity − Terabytes or petabytes are typical storage capabilities for tertiary storage systems. Long-term data retention is possible with them.

Archival and Backup − Archival data is held in tertiary storage for lengthy periods and accessed rarely. Additionally, it is utilised for disaster recovery data backup.

Reliability − Tertiary storage media can preserve data for long periods without degradation due to its durability and longevity.

Offline Storage − Offline or near-line tertiary storage keeps media from rotating or being instantly accessible. They are loaded or mounted as needed.

Cost-Effective − Tertiary storage is cost-effective for massive, infrequently accessed data. Media are cheaper than high-speed, high-capacity disc drives.

Scalability − Users are able to adjust the amount of data they store in the cloud to meet their requirements because to the cloud’s high degree of scalability. This elasticity is advantageous for firms that have storage requirements that are subject to change.

Accessibility − If you have access to the internet, you can retrieve data saved on the cloud from anywhere. Because of this, it is much simpler for individuals and organisations to access their data using a variety of devices, such as personal computers, smartphones, and tablets.

Cost-effectiveness − Cloud storage generally charges users for the storage capacity and resources they use. This may be cheaper than updating on-premises storage.

Security − The security of user data is a top priority for cloud storage providers. This consists of access controls, frequent security audits, and the encrypting and decrypting of data at all times. Users must take responsibility for the security and configuration of their data in the cloud.

Backup and Disaster Recovery − Cloud storage services have backup and restore tools built in. Users can set up regular backups and recover data in case they lose data or the system breaks down.