Storage
There are number of different technical terms used to define and differentiate hard drives. Cached memory, NCQ, S-ATA, P-ATA, SMART, SCSI, AAM, rotation speed, etc. All of these terms can be a little confusing so in this article we will explain what they all mean.
The structure of a hard drive is divided into three parts. The first is presented in the form of superimposed platters which is composed of glass or aluminium. Each platter has two faces that are magnetised (other layers are also used) and are used to record information in binary format (0 and 1, called bits). This binary system can be physically translated by a charge (or state). We use the negative charge to define the 0’s and a positive charge to define the 1’s.
Each platter turns on an axis using ball bearings or oil at a consistent speed (angular speed) in a counter clockwise direction.
Most 3 and a half inch hard drives turn at a speed of 7200 revolutions per minute, with most 2 and a half inch drives rotating at 4200 or 5400 rpm with SCSI and SAS drives turning at 10000 rpm.
When the platter is spinning it creates a thin layer of air (in the order of a micron) on which it places the read/write heads. If a small grain of dust was to get onto the platter or the read/write head then the hard drive would be permanently damaged. This is why they are closed firmly in a solid metal casing that is free of air. These cases can not be opened as you will risk damaging the disk, even if you wanted to install a Plexiglass so that you can watch it turning.
To organise the saved data, each platter is divided into tracks that circulate the platter and which are cut at regular intervals into equal sizes called sectors (or blocks). This physical organisation is done by low level formatting the disk so that the Master boot Record (MBR) can be constructed, which will represent the first sector of the hard drive (cylinder 0, head 0 and sector 1). The MBR integrates the Master Boot Code (MBC) and the partition tables. This also contains information referencing the manufacturer (number of bytes per sector, serial number, etc).
You should therefore not confuse the low level format, which will take hours depending on the size of the drive, with the logical format that is used to create your file system (FAT32, NTFS, Ext2, Ext3, ReiserFS, etc) which will be necessary for your operating system to be able to store and use its files.
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