Understanding posts written about hard disk drives can be confusing to people who aren't familiar with the Data Recovery industry's basic language. But the terms are essentially easy to understand. The following are a few of the most used hard drive terms:
Platter
Within the sealed unit of your computer's hard drive (s) are a few platters, or plates, attached to a fixed shaft, attempting to find all intents and purposes like an old record player with a pile of records waiting to be played. In the case of hard disk drives ,however ,the platters are not touching one another but are instead separated by an exact amount of space. Each platter has a top side and a bottom side, and these sides are lined with an easily magnetized substrate. The top side of a platter is Side 0 and the underside is Side 1. When power is applied to the disk drive, the spindle turns at a fixed high rate of speed, thus causing the platters to spin.
Tracks
Each platter contains concentric circles called tracks. Tracks are numbered from the outside in, with the outlying track being track 0 on each side of a platter. So for a hard drive having 12 tracks, track 0 would be the outlying track and track 11 would be the one nearest the shaft.
Cylinders
A cylinder is composed of the same track on both sides of all platters. Therefore using the example of a hard disk having 12 tracks per side on its platters, cylinder 0 would be composed of all of the outermost tracks, and cylinder 11 would consist of all of the innermost tracks.
Sectors
To gain order in the storage of information on the platters, the platters are electronically split into pie-shaped wedges called sectors. Sectors are where the data is stored. Each sector holds 512 bytes of information and has a unique address, just like a home in a neighbourhood. A sector's address is composed of the platter number, the platter's side number, the track number, and the sector number on that track.
Clusters
The 512-byte sectors are commonly grouped into clusters for easier manipulation. One partitioning scheme uses cluster sizes of 4K, while another uses 32K clusters. Some operating systems permit the user to pick the cluster size, although one special size will customarily be recommended by the operating software manufacturer.
Heads
Heads are the devices used to pen and read data onto and from the hard disk drive's platters. Each head is attached to an arm which moves the head into position over a particular sector or cluster, and consists of just about nothing less than a tiny coil of wire embedded into a ceramic housing. In Write mode, when the coil is energised in one specific direction, the head "writes" a 0 onto the platter's substrate underneath it; that is, it polarizes a little section of the disk platter in a certain direction. Energize the coil in the other direction, and the head "writes" a 1. In Read mode, the coil senses the polarization of the information bit on the platter as it spins past, and it transfers that information back to the read/write circuitry.
Head Crash
The read/write heads actually float above the spinning platters on a bed of air created by the spinning of the platters. When something happens to cause the heads to overcome the centrifugal force of the platter's spin, the heads can get in contact with the platters, resulting in what is known as a head crash or Head-To-Disk-Interference. This is generally catastrophic, as the heads will actually scrape the magnetic substrate right off the platters, destroying information irrevocably. Rescuing info after a head crash is very difficult and slow and therefore quite costly. Normally you'll need to employ a data recovery expert for a hard drive repair as this isn't a fault you can fix yourself.
Platter
Within the sealed unit of your computer's hard drive (s) are a few platters, or plates, attached to a fixed shaft, attempting to find all intents and purposes like an old record player with a pile of records waiting to be played. In the case of hard disk drives ,however ,the platters are not touching one another but are instead separated by an exact amount of space. Each platter has a top side and a bottom side, and these sides are lined with an easily magnetized substrate. The top side of a platter is Side 0 and the underside is Side 1. When power is applied to the disk drive, the spindle turns at a fixed high rate of speed, thus causing the platters to spin.
Tracks
Each platter contains concentric circles called tracks. Tracks are numbered from the outside in, with the outlying track being track 0 on each side of a platter. So for a hard drive having 12 tracks, track 0 would be the outlying track and track 11 would be the one nearest the shaft.
Cylinders
A cylinder is composed of the same track on both sides of all platters. Therefore using the example of a hard disk having 12 tracks per side on its platters, cylinder 0 would be composed of all of the outermost tracks, and cylinder 11 would consist of all of the innermost tracks.
Sectors
To gain order in the storage of information on the platters, the platters are electronically split into pie-shaped wedges called sectors. Sectors are where the data is stored. Each sector holds 512 bytes of information and has a unique address, just like a home in a neighbourhood. A sector's address is composed of the platter number, the platter's side number, the track number, and the sector number on that track.
Clusters
The 512-byte sectors are commonly grouped into clusters for easier manipulation. One partitioning scheme uses cluster sizes of 4K, while another uses 32K clusters. Some operating systems permit the user to pick the cluster size, although one special size will customarily be recommended by the operating software manufacturer.
Heads
Heads are the devices used to pen and read data onto and from the hard disk drive's platters. Each head is attached to an arm which moves the head into position over a particular sector or cluster, and consists of just about nothing less than a tiny coil of wire embedded into a ceramic housing. In Write mode, when the coil is energised in one specific direction, the head "writes" a 0 onto the platter's substrate underneath it; that is, it polarizes a little section of the disk platter in a certain direction. Energize the coil in the other direction, and the head "writes" a 1. In Read mode, the coil senses the polarization of the information bit on the platter as it spins past, and it transfers that information back to the read/write circuitry.
Head Crash
The read/write heads actually float above the spinning platters on a bed of air created by the spinning of the platters. When something happens to cause the heads to overcome the centrifugal force of the platter's spin, the heads can get in contact with the platters, resulting in what is known as a head crash or Head-To-Disk-Interference. This is generally catastrophic, as the heads will actually scrape the magnetic substrate right off the platters, destroying information irrevocably. Rescuing info after a head crash is very difficult and slow and therefore quite costly. Normally you'll need to employ a data recovery expert for a hard drive repair as this isn't a fault you can fix yourself.
About the Author:
Jason Sloan runs a data recovery business called Kingdom Data Recovery Edinburgh who service all the United Kingdom. He's got many articles on his web site which refer to issues with storage and useful information about preventing data loss.
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