Hard Drive Glossary

Hard Drive Glossary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Notice: The information provided herein is presented as is and without any warranty of any kind, either expressed or implied. In no event will DEW Associates Corporation be liable to you for any damages, including any loss of profit or other money damages, arising out of the use or inability to use the information contained herein. We make no representations or warranties with respect to the contents hereof and specifically disclaims any implied warranties of merchantability or fitness for any particular purpose. Any parameters and specifications provided are subject to change without notice.

– H –
HARD ERROR
An error that cannot be overcome by repeated readings and repositioning of the heads.

HARD SECTORED
A technique where a digital signal indicates the beginning of a sector on a track. This is in contrast to soft sectoring, where the controller determines the beginning of a sector by the reading of format information from the disk.

HEAD
The electromagnetic device that write (records), reads (plays back), and erases data on a magnetic media. It contains a read core(s) and/or a write core(s) and/or erase core(s) which is/are used to produce or receive magnetic flux. Sometimes the term is all inclusive to mean the carriage assembly which includes the slider and flexure.

As a side note, on the 80000 & 90000 series Maxtor drives the model number contains the number of heads and surfaces in use on that particular model. For instance, the trailing number in model number 88400D8 tells us that this drive uses 8 surfaces (4 platters) and 8 heads. In some models, like the 84320D5, the drive is using 5 surfaces (3 platters) and 5 heads. One side of one platter is not being used in models with odd surface numbers.

HEAD CRASH
The inadvertent touching of a disk by a head flying over the disk (may destroy a portion of the media and/or the head).

HEAD DISK ASSEMBLY (HDA)
The mechanical portion of a rigid, fixed disk drive. It usually includes disks, heads, spindle motor, and actuator.

HEAD LOADING ZONE
The non-data area on the disk set aside for the controlled takeoff and landing of the Winchester heads when the drive is turned on and off. Dedicated annulus on each disk surface in which heads are loaded, unloaded, or flying height is established. Head-disk contact may occur in some instances; no data is recorded in this area.

HEAD POSITIONER Also known as an actuator, a mechanism that moves the arms that carry read/write heads to the cylinder being accessed.

– I –
Integrated Drive Electronics (IDE)
The most common interface standard for connecting hard-disk drives to PCs. Also known as: ATA. See Also Enhanced IDE, and ATAPI.

INDEX
Similar to a directory, but used to establish a physical to logical cross reference. Used to update the physical disk address (tracks and sectors) of files and to expedite accesses.

INSIDE DIAMETER
The smallest radial position used for the recording and playback of flux reversals on a magnetic disk surface.

INITIALIZATION
Applying input patterns or instructions to a device so that all operational parameters are at a known value.

INPUT
Data entering the computer to be processed; also user commands or queries.

INPUT/OUTPUT (I/O)
The process of entering data into or removing data from a computer system or a peripheral device.

INTELLIGENT PERIPHERAL
A peripheral device that contains a processor or microprocessor to enable it to interpret and execute commands.

INTERFACE
The data transmitters, data receivers, logic, and wiring that link one piece of computer equipment to another, such as a disk drive to a controller or a controller to a system bus.

INTERFACE STANDARD
The interface specifications agreed to by various manufacturers to promote industry-wide interchangeability of products such as a disk drive. Interface standards generally reduce product costs, allows buyers to purchase from more than one source, and allow faster market acceptance of new products.

INTERLEAVE
An ordering of physical sectors to be skipped between logical sectors on your hard disk. On all IDE drives the Interleave is optimized 1:1.

I/O PROCESSOR
Intelligent processor or controller that handles the input/output operations of a computer.

INTERRUPT A signal, usually from a subsystem to a central processing unit, to signify that an operation has been completed or cannot be completed.

– J –
JUMPER
Essentially a simple on/off switch in which a plastic-covered metal jumper is placed over two pins to close a circuit. Jumpers are usually used to set a device’s attributes. In the case of most hard drives, a jumper is used to enable options like Master/Slave, Cable Select or 4096 cylinder truncation.

Inserting a jumper from the top row to the bottom row enables the option for that particular position. The bottom row of pins are active, and the top row of pins (identified by the one missing pin in that row) are all grounded (inactive). It is safe to “store” unused jumpers sideways in this upper row.

J1 EIDE INTERFACE CONNECTOR
This is the connector where the ribbon cable attaches to go from the hard drive to the IDE connector on your computer’s motherboard or the IDE hard drive interface card. This connector is keyed and will only fit one way. Do not force the connector. The striped or colored edge of the IDE interface cable indicates pin 1. Pin 1 on the IDE interface cable should match pin 1 on the drive connector. Pin 1 is usually closest to the power connector.

J2 POWER CONNECTOR Connect an available power connector to J2 on the hard drive. This connector is keyed and will only fit in one orientation. Do not force the connector. IMPORTANT: After attaching the IDE interface cable and the power cable to the hard drive, verify that all other cables connected to other devices, the mother board or interface cards are correctly seated and haven’t been moved as the result of your installing a new drive or cable.

– K –
KILOBYTE (KB)
A unit of measure of approximately 1,000 bytes. (However, because computer memory is partitioned into sizes that are a power of two, a kilobyte is really 1,024 bytes.) See Decimal vs. Digital for further details.
 
– L –
LANDING ZONE, LZONE OR LZ
Also known as the parking cylinder or parking zone. The Landing Zone is a “safe” area on inside tracks of the drive where the read/write heads are moved when the power is turned off. The heads are magnetically latched when they get there (sometimes you can hear a small click). All modern IDE drives park automatically on power down, so manually parking the heads is no longer necessary. This setting is usually set to 0. Some systems with “Auto Detect” set this to 65,535, or equal to the number of cylinders, any of these settings is fine.

LATE BIT
A bit that is in the late half of the data window.

LATE WINDOW
A data window that has been shifted in a late direction to facilitate data recovery.

LATENCY
A delay encountered in a computer when waiting for a specific response. In a disk drive there is both seek latency and rotational latency. The time required for the addressed sector to arrive under the head after the head is positioned over the correct track. It is a result of the disk’s rotational speed and must be considered in determining the disk drive’s total access time.

LOGIC
Electronic circuitry that switches on and off (“1” and “0”) to perform functions.

LOGICAL ADDRESS
A storage location address that may not relate directly to a physical location. Usually used to request information from a controller, which performs a logical to physical address conversion, and in turn, retrieves the data from a physical location in the mass storage peripheral.

LOGICAL BLOCK ADDRESSING (LBA)
Defines the addressing of the device by the linear mapping of sectors. The Logical Block Address (LBA) mode can only be utilized in systems that support this form of translation. The Cylinder, Head and Sector (CHS) geometry of the drive, as presented to the host, differs from the actual physical geometry.

The host AT computer may access a set parameters for a drive such as the: number of cylinders, heads and sectors per track, plus cylinder, head and sector addresses. However, the drive can’t use these host parameters directly because of zone density recording techniques. The drive translates the host parameters to a set of logical internal addresses for data access.

The host drive geometry parameters are mapped into an LBA based on this formula:

LBA = (HSCA – 1) + HHDA x HSPT + HNHD x HSPT x HCYA   (1)
       = (HSCA – 1) + HSPT x(HHDA + HNHD x HCYA)              (2)
Where:   HSCA = Host Sector Address
  HHDA = Host Head Address
  HCYA = Host Cylinder Address
  HNHD = Host Number of Heads
  HSPT = Host Sector Per Track

The LBA is first checked for drive capacity violations. If it there are none, the LBA is converted to physical drive cylinder, head and sector values. The physical address is then used to access or store the data on the disk and for other drive related operations.

LOGICAL SECTOR
The lowest unit of space that DOS can access through a device driver; one or more physical sectors.

LOW FREQUENCY The lowest recording frequency used in a particular magnetic recording device. With FM or MFM channel codes this frequency is also called “IF”.

– M –
MAIN MEMORY
Random-access memory (RAM) used by the central processing unit (CPU) for storing program instructions and data currently being processed by those instructions. (See also random access memory.)

MASS STORAGE
Auxiliary memory used in conjunctions with main memory; generally having a large, on-line storage capacity.

MASTER/SLAVE (M/S)
This is also known as dual drive support. Two drives may be accessed via a common interface cable, using the same range of I/O addresses. The jumpers on the drive are set to device 0 or 1 (Master/Slave), and are selected by the drive select bit in the Device/Head register of the task file.

All task file registers are written in parallel to both drives. The interface processor on each drive decides whether a command written to it should be executed, which depends on the type of command and which drive is selected. Only the drive selected executes the command and activates the data bus in response to host I/O reads. The drive not selected remains inactive.

A Master/Slave relationship exists between the two drives on the same bus, device 0 is the Master and device 1 is the Slave. Using a Maxtor hard drive as an example, when the master/slave jumper is closed (factory default), the drive assumes the role of Master; when those same jumpers are left open, the drive acts as a Slave. In single drive configurations, the jumper must be closed.

MAXBLAST
Maxtor provides an outstanding installation software package with its drives called MaxBlast, and it comes on a bootable diskette. The self-booting feature is provided by the Micro House Operating System (MHOS) that runs the EZ-MAX software. There are two utilities that come with MaxBlast, they are EZ-Max and EZ-Drive.

EZ-Max is a utility that has been designed to allow users to quickly and easily install new Maxtor IDE hard drives. It will automatically identify the attached hard drives, (such as Model, Serial Number, Cylinders, Heads, and Sectors.) analyze the system BIOS, (such as the date of the BIOS build, manufacturer, etc..), the system processor type, and if the user requests, launch the EZ-Drive program.

The EZ-Drive program will automatically detect the status of the hard drive and advise the user of installation options. It will partition, format, and if desired, transfer the operating system to the new drive. EZ-Drive will also detect if the BIOS is unable to properly control the drive, and install EZ-BIOS if such support is needed.

MAXBLAST PLUS
MaxBlast is the newest on the Maxtor installation utilities. Like the earlier version, there are two utilities that come with MaxBlast Plus, EZ-Max and EZ-Drive. EZ-Max is a utility that has been designed to allow users to quickly and easily install new Maxtor IDE hard drives. It will automatically identify the attached hard drives, (such as Model, Serial Number, Cylinders, Heads, and Sectors.) analyze the system BIOS, (such as the date of the BIOS build, manufacturer, etc..), the system processor type, and if the user requests, launch the EZ-Drive program. The EZ-Drive program will automatically detect the status of the hard drive and prompt the user of their installation options. It will partition, format, and if desired, transfer the operating system to the new drive. EZ-Drive will also detect if the BIOS is unable to properly control the drive, and install EZ-BIOS if such support is needed.

What differentiates MaxBlast Plus from MaxBlast:

  • Friendly GUI Interface with mouse support.
  • Comprehensive Pre-Installation Screens that give the steps needed to physically install your Maxtor Hard Drive. These screens can be accessed from the MaxBlast Plus diskette EVEN if your hard is NOT installed in your computer.

MEAN TIME BETWEEN FAILURES (MTBF)
MTBF ratings are measured in hours and indicate the durability of hard disk drives.

Most new drives to have MTBF ratings of 500,000 hours or more. This means that approximately half of the disk drives with such a rating will fail once in the first 500,000 hours of operation. Most working conditions are not ideal, so MTBF ratings can be considered as only approximate guideline for determining the longevity of disk drives. The fact that MTBF ratings exist at all, however, underscores the fact that every disk drive will eventually fail if run long enough.

Most manufacturers do not differentiate between various usage profiles (e.g., power-on hours, power saving modes, non-operating periods or operating temperatures within the published specification.)

MEGABYTE (MB)
A confusing term, it can mean either 1,000,000 bytes decimal (106) or 1,048,576 bytes digital (220). Maxtor defines 1MB as 1,000,000 bytes. See: Decimal vs. Digital for further details.

MEMORY
Any device or storage system capable of storing and retrieving information. (See also storage definitions.)

MICROCOMPUTER
A computer whose central processing unit is a microprocessor. It is usually, but not necessarily, desktop size.

MICROPROCESSOR
A central processing unit (CPU) manufactured as a chip or a small number of chips.

MISSING PULSE
A term used in surface certification. It is when a prerecorded signal is reduced in amplitude by a certain specified percentage.

MODEL NUMBER
All hard drives have model numbers that contain allot of descriptive information about the drive. 

MODIFIED FREQUENCY MODULATION (MFM)
A method of encoding digital data signals for recording on magnetic media. Also called “three frequency recording”. Recording code that only uses synchronizing clock pulse if data bits are not present. Doubles the lineal bit density without increasing the lineal flux reversal density, compared to Frequency Modulation.

MODIFIED MODIFIED FREQUENCY MODULATION (MMFM)
A recording code similar to MFM that has a longer run length limited distance.

MODULATION 1. Readback voltage fluctuation usually related to the rotational period of a disk. 2. A recording code, such as FM, MFM, or RLL, to translate between flux reversals and bits or bytes.

– N –
NON-RETURN TO ZERO A form of data encoding that is not self-clocking, in other words, it needs to be provided with an external bit cell clock signal. Generally used in higher-performance disk drives.
– O –
OFF-LINE
Processing or peripheral operations that occur when the drive is not being accessed by the system CPU via the system bus.

ON-LINE
Processing or peripheral operations that occur when the drive is being accessed by the system CPU via the system bus.

OPEN LOOP SERVO
A head positioning system that does not use positional information to verify and correct the radial location of the head relative to the track. This is usually achieved by use of a stepper motor which has predetermined stopping point that corresponds to track locations.

OPERATING SYSTEM
A software program that enables the computer and its peripheral devices to interact with the user. (See disk operating system.)

OUTSIDE DIAMETER
The largest radius recording track on a disk.

OVERHEAD
The amount of extra activity it takes to perform a specific function. In the case of hard disk drive activity, there are several factors such as latency, settling time, servo overhead, and many others. These delays must be factored in when determining how long any read, write, or seek may take.

OVERWRITE A test that measures the residual 1F recorded frequency on a track after being overwritten by a 2F signal. Variations of the test exist.

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