概述
程序员应该更加深入的理解一个计算机系统，包括它的硬件系统和软件系统。今天一起看看计算机内部的硬盘(我们主要看的是传统的磁盘)的构造以及它与主板的接口主要有哪些。这里主要是介绍一下硬件系统，不涉及与磁盘息息相关的文件系统(file system)。
磁盘的构造
A hard disk drive (HDD) is a data storage device used for storing and retrieving digital information using one or more rigid (“hard”) rapidly rotating disks (platters) coated with magnetic material. The platters are paired with magnetic heads arranged on a moving actuator arm, which read and write data to the platter surfaces.Data is accessed in a random-access manner, meaning that individual blocks of data can be stored or retrieved in any order rather than sequentially. HDDs retain stored data even when powered off.
一图胜千言，这张图找了半天，上图：
磁盘与主板之间的接口
硬盘与主机系统的系统总线通过特定的传输接口相连。
IDE and SATA are different types of interfaces to connect storage devices (like hard drives) to a computer’s system bus. SATA stands for Serial Advanced Technology Attachment (or Serial ATA) and IDE is also called Parallel ATA or PATA. SATA is the newer standard and SATA drives are faster than PATA (IDE) drives. For many years ATA provided the most common and the least expensive interface for this application. But by the beginning of 2007, SATA had largely replaced IDE in all new systems.
The ATA interface (ATA stands for AT attachment where “AT” refers to IBM’s PC/AT for which it was originally built) evolved in stages from Western Digital’s original Integrated Drive Electronics (IDE) interface. After the introduction of Serial ATA in 2003, the original ATA was retroactively renamed Parallel ATA.
磁盘分区
磁盘分区的重要性在于
保证数据的安全性，由于每个分区的数据是分开的，相对处在一种比较独立的状态下，因此，当需要对某个分区的数据重整时，如，重装系统，你只需要将装载系统的那个磁盘里的重要文件事先备份到其他分区。
分区后系统性能会更好。由于分区会将数据集中在某个柱面(cylinder)的特定的区段，当读写特定分区的数据的时候，只用搜寻对应的柱面范围即可，而不必全盘检索，这就大大提高了数据读取的速度和性能。
固态硬盘
现在大家最喜爱的硬盘是固态硬盘。那么固态硬盘与我上面说的，构造有些不同。
SSDs have no moving (mechanical) components. This distinguishes them from traditional electromechanical magnetic disks such as hard disk drives (HDDs) or floppy disks, which contain spinning disks and movable read/write heads.固态硬盘的价格更高，抛开价格因素不谈，固态硬盘的性能更优，只是由于闪存的次数是有限的，因此，固态盘的寿命对于那些发烧级的电脑用户来说有点遗憾，不过，现在的固态硬盘的技术都足以确保大多数情况下，你的硬盘还好好的，你却已经爱上了别的一款性能更优的超极本。
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