| A hard disk drive (HDD), hard disk, hard drive or fixed disk is a data storage device that uses magnetic storage to store and retrieve digital information using one or more rigid rapidly rotating disks (platters) coated with magnetic material. |
硬盘驱动器（HDD)，硬盘，硬驱或固盘，是一种数据存储设备，利用一片或多片高速旋转的带有磁性涂层的圆盘，使用磁纪录的原理来记录和提取数字信息。 |
| The platters are paired with magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces. |
圆盘有磁头相辟配，通常装置于一个活动的执行器臂上，在磁盘表面上进行数据读写。 |
| Data is accessed in a random-access manner, meaning that individual blocks of data can be stored or retrieved in any order and not only sequentially. |
数据是以随机的方式进行读写，意思就是，每一个数据块可以以任意的顺序进行储存或读取，不需要按顺序操作。 |
| HDDs are a type of non-volatile storage, retaining stored data even when powered off. |
硬盘是一种永存式存储器，即使在电源关闭后仍然保存着已存储的数据。 |
| Introduced by IBM in 1956, HDDs became the dominant secondary storage device for general-purpose computers by the early 1960s. |
1956年由IBM公司引入，到20世纪60年代初期，即成为通用计算机主要的辅助存储装置。 |
| Continuously improved, HDDs have maintained this position into the modern era of servers and personal computers. |
经过不断的改进，直到现代的服务器和个人电脑时代，硬盘一直保持这一地位。 |
| More than 200 companies have produced HDDs historically, though after extensive industry consolidation most current units are manufactured by Seagate, Toshiba, and Western Digital. |
历史上，有两百多家公司生产过硬盘，但经过大规模的工业合并，现在大部分的硬盘都是由西捷，东芝和西部数据生产的。 |
| HDD unit shipments and sales revenues are declining, though production (exabytes per year) is growing. |
硬盘的出货量和销售收入在持续下降，尽管生产量（按每年的艾字节计算）仍在增长。 |
| Flash memory has a growing share of the market for secondary storage, in the form of solid-state drives (SSDs). |
闪存以固态驱动器（SSD）的形式，不断地扩张辅助存储器市场的份额。 |
| SSDs have higher data-transfer rates, higher areal storage density, better reliability, and much lower latency and access times. |
SSD的数据传送率更快，单位存储密度更高，可靠性更好，以及更短的时延和读写时间。 |
| Though SSDs have higher cost per bit, they are replacing HDDs where speed, power consumption, small size, and durability are important. |
尽管按比特来算，SSD价格更高，但在更需要考虑速度、能耗、体积和可靠性的地方，SSD正在取代硬盘。 |
| The primary characteristics of an HDD are its capacity and performance. |
硬盘最大的特点是容量和性能。 |
| Capacity is specified in unit prefixes corresponding to powers of 1000: a 1-terabyte (TB) drive has a capacity of 1,000 gigabytes (GB; where 1 gigabyte = 1 billion bytes). |
容量的衡量单位是以千的幂次为单位：一个太字节（TB）的硬盘容量是一千个吉字节（GB；在此，一吉字节等于十亿字节）。 |
| Typically, some of an HDD's capacity is unavailable to the user because it is used by the file system and the computer operating system, and possibly inbuilt redundancy for error correction and recovery. |
通常，硬盘有部分容量是用户无法用到的，因为它是由文件系统和电脑操作系统占用了，还有可能是用于错误校正和恢复的内建冗余。 |
| Performance is specified by the time required to move the heads to a track or cylinder (average access time) plus the time it takes for the desired sector to move under the head (average latency, which is a function of the physical rotational speed in revolutions per minute), and finally the speed at which the data is transmitted (data rate). |
性能的衡量由几部分组成，一是把磁头移动至某一磁道即柱面的时间（平均读写时间），加上所要的扇区移动至磁头下方的时间（平均时延，这是物理转速的函数，以每分钟的转数有关），最后，数据传送的速度（数据速率）。 |
| The two most common form factors for modern HDDs are 3.5-inch, for desktop computers, and 2.5-inch, primarily for laptops. |
现代硬盘最普遍的尺寸格式为用于台式机的3.5吋，和主要用于笔记本电脑的2.5吋。 |
| HDDs are connected to systems by standard interface cables such as PATA (Parallel ATA), SATA (Serial ATA), USB or SAS (Serial attached SCSI) cables. |
硬盘与系统的连接使用标准的接口电缆，诸如PATA（平行ATA），SATA（串行ATA），USB或SAS（串行连接小型计算机系统接口）电缆。 |
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