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HARD DRIVES
Inside the Hard Drive:All hard drives are alike in that each is composed of individual disks,or platters,with read/write heads
on actuator arms controlled by a servo motor - all contained in a sealed case that prevents contamination by outside air.The
platters are made of aluminum and are coated with a magnetic media,usually cobalt or ferro-ceramics.There are two tiny read/write
heads for each platter,one to read the top and the other to read the bottom of the platter.The coating on the platters is
phenomenally smooth.It has to be as the read/write heads actually " float " on a cushion of air above the platters,spinning
at speeds measured in rpm`s.
TRACKS
The physical area that contains the data.Are a concentric circular area of the disk that is discrete to all other tracks.A
lenght of a track is one circumference of the disk.On a hard drive,there may be 1,000 or more tracks. When data is written
to the disk,it begins with the outer most track first.
SECTORS
The smallest unit that can be accessed on a disk.A single segment of a disk created by cross-sectioning divisions that intersect
all the tracks.In addition to dividing each track into manageable pieces,sectors provide adddressing references. Data can
be addressed by its track and sector numbers.
CYLINDERS
The set of tracks that are aligned vertically on platters and that are not accessible without head movement in a hard disk
drive. Units of data that are related to one another are placed in cylinders so that they may be read faster and so that they
require less head movement.
PLATTERS
A disk in a hard drive onto which data is written.
HARD DRIVE RELATED TERMINOLOGY:
IDE:
Intelligent Drive Electronics or Integrated Drive Electronics,
depending on who you ask.An IDE interface is an interface
for mass storage devices, in which the controller is integrated into the disk.
EIDE:
Enhanced IDE, a newer version of the IDE mass storage device interface standard. Not only are they faster than the old IDE.
But also hold more storage.
PARTITION
To divide memory or mass storage into isolated sections. In DOS systems, you can partition a disk, and each partition will
behave like a separate disk drive.
PRIMARY PARTITION
Partition used to boot the system,it stores the OS.A hard drive can be divided into a maximum of four primary partitions.(
however in DOS one must be active partition )
EXTENDED PARTITION
Any other partition on a hard drive. Can be used for other OSs or subdivided further ( up to 23 more times).
FORMAT
To prepare a storage medium by defining tracks and sectors where data will be placed in compliance with a specific operating
systems requirements.
LANDING ZONE:
A non-data space on a computer's hard disk where the read/write heads rest,or park, when the computer's power is turned off.
LBA,logical block addressing
A method used with SCSI and IDE disk drives to translate the cylinder, head, and sector specifications of the drive into addresses
that can be used by an enhanced BIOS. LBA is used with drive's that are larger than 528 MB. CMOS routines that allow the hard
drive to lie to the computer about its geometry.
ECHS:
Enhanced Cylinder,Head,and Sectors, basically the same as LBA but more advanced.
INT 13 EXTENSIONS:
New set of BIOS commands that break the 8.4 gig barrier by allowing more than 1024 cylinders. A system with INT13 can handle
drives up to well over 100 gigabytes.
PIO MODES:
Programmable Input/Output modes are standardized protocols that allow ATA(IDE) drives to transfer data to and from the hard
drive and memory
DMA MODES:
Direct Memory Access is a data transfer method that bypasses the CPU and transfers data directly into memory, leaving the
CPU free to run programs
HIGH LEVEL FORMAT:
Performed by DOS/Windows commands to prepare the disk partitions for use by the OS and to store data.
VOICE COIL MOTOR:
A device that moves a disk-drive actuator arm using electromagnetism. Faster than the stepper and automatically parks the
heads.
BOOT SECTOR:
The special sector the computer boots to first on the hard drive. Which contain two critical pieces of info : The Master Boot
Sector ( MBR ) and the Partition Table
S.M.A.R.T.:
Self Monitoring Analysis and Reporting Technology. It gives the disk drive the ability to send information to the PC?s operating
system when its operation is degrading for any reason. All modern Hard drive.
ACCESS TIME:
The time required to locate and load data from storage after the seek command is issued.
SEEK TIME:
The average time required to locate specific data on a disk.
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