Glossary & Terms:

AV Professional
The meet the demands of the digital AV industry, Hard Drive manufacture's created a standard in which scsi/ide drives must perform in order to ensure uninterrupted data transfers. The following standard must apply in order to meet specifics: AV customization takes place in the following mode sense pages:
• Error Recovery
• Disconnect/Reconnect
• Cache Configuration
• Error Logging
• S.M.A.R.T
• Adjustable retries

Average Seek Time
The average time required for the heads to move from one track to any other track.

Cache Buffer
A bank of solid-state memory inside the drive that stores some data from the discs. The system may then refer to this memory for information instead of going to the media, increasing the processing speed.

Capasity
The total amount of data that can be stored on a device, usually measured in megabytes or gigabytes.

Cluster Size
The number of sectors that the operating system allocates each time disc space is needed.

DAT (Digital Audio Tape)
Storage device that records digital information on a magnetic tape 4 mm wide.

Data-Transfer Rate
Speed at which bits are sent. In a disc storage system, the communication is between the CPU and the controller. plus the controller and the disc drive. Typical units are mega bits-per-secofld - also known as megahertz (MHz). Internal data- transfer rate is the rate that data is written to and read from the discs.

DDS (digital data storage)
A (rata-storage format that was developed from digital audio tape (DAT) to reliably store computer data. DDS is defined by international standards and is supported by many manufacturers, but more importantly, it is subject to thorough collaborative testing programs, which ensure that tapes (or media) written by one manufacturer's drives can be read by those of other manufacturers.

Differential SCSI
The Differential SCSI interface allows longer cable lengths from the drive to the host with no degradation of data. It is ideal for mainframe, RAID and server applications.

Enhanced IDE
A high-speed, low-cost interface to connect up to 4 devices found on 99% of PCs - usually hard disc, tape drive and CD-ROM.

Error-Correction Code (ECC)
ECC provides 72-bit on-the-fly hardware correction for excellent performance, and 144-bit firmware correction verifies that data is being read correctly within each sector.

Fast ATA-2/ATA-3 Enhanced IDE
Desktop drive interfaces that support the industry-standard PIO Mode 4 and DMA Mode 2 protocols. This enables data-transfer rates of up to 16.6 Mbytes/sec.

Fast Wide SCSI-2
The fast Wide SCSI-2 interface provides a 16-bit wide SCSI bus, compared to the normal Fast SCSI-2, 8-bit SCSI bus. The wider 16-bit bus provides a transfer rate of 20 Mbytes per second compared to 10 Mbytes per second with Fist SCSI- 2 8-bit interfaces.

Fibre Channel
The Fibre Channel Interface is an American National Standards Institute (ANSI) serial interface. The FC-AL interface was created to answer the need for a pluggable disc drive that offers both hot pluggability and loop resiliency at an economical cost. The interface has the capability of transferring data up to 100 Mbytes per second, and 200 Mbytes per second dual loop. It can operate over copper and fibre optic cabling at distances up to 10 kilometers. The Fibre Channel interface is ideal for storage, video, graphic, and mass data-transfer applications Fibre Channel also supports up to 126 devices on a signal node, which is ideal for large RAID subsystems.

File Allocation Table (FAT)
The operating system's method to keep track of which clusters are allocated to which files and which are available for use.

Firmware
A computer program written into a storage medium that cannot be accidentally erased, such as ROM. It can also refer to devices containing such programs.

Flip Chip
Technology that reduces semiconductor packaging. It is used with flex circuits to reduce mass.

Gigabyte (Gbyte)
1,000 Mbytes or 1,000,000,000 bytes.

Half-height Drive
A drive that is 1.63 inches high.

Hot-plug Capability
A feature on many SCSI drives that allows removal and replacement of drives without shutting the system down. This is especially valuable in drive array systems.

Input/output (I/0)
The process of entering data into or removing data from a computer system.

Interleaving
The interleave value tells the controller where the next logical sector is located in relation to the current sector. Interleaving is used to improve the system throughout based on overhead time of the host software, the disc drive and the controller.

Latency (rotational)
The average time required for the disc to rotate to a desired sector On average, latency is the time for half of a disc revolution.

Mean Time Between Failure (MTBF)
A statistical calculation or number that loosely denotes the reliability of a drive. The higher the MTBF, the more reliable the drive is expected to be.

Megabyte (Mbyte)
1) 1,048,576 bytes for semiconductor memory 2) 1,000,000 bytes for drive capacity.

Operating System
An operating system is a program that acts as an interface between the user of a computer and the computer hardware. The purpose of the operating system is to provide an environment in which a user can run programs.

Partitioning
A method for dividing an area on a disc drive for use by more than one disc operating system or for dividing large disc drives into areas that the File Allocation Table (FAT) can deal with when in use. This limit can be overridden using partitioning software written for this purpose.

Printed Circuit Board (PCB)
The circuit board with the chips attached.

Printed Wire Assembly (PWA)
A completed circuit board with components installed. (Same as PCB)

Printed Wire Board (PWB)
A circuit board without components installed, also known as a bare board.

QIC
Quarter-Inch-Cartridge, Defines a standards committee and tape media.

RAID Systems
RAID (redundant array of independent discs) is a concept in storage subsystems that can deliver higher levels of protection against downtime and data loss than conventional disc drives. RAID refers to a drive architecture designed to safeguard critical data through redundancy. In theory, RAID arrays composed of conventional discs can function for hundreds or even thousands of years without losing data because of a disc failure. RAID also offers other benefits: it can improve input/output performance, make servicing simpler and quicker and allow users to fine-tune the drive system to match the needs of specific applications. Level 0 distributes data across discs by striping - a technique for storing consecutive chunks of.data on different discs. Striping improves 1/0 throughput but provides no more data protection than conventional drives. Level I achieves data redundancy through mirroring - keeping identical data on two separate discs. Mirroring offers excellent reliability and some improvement in 1/0 throughput but is relatively inefficient in its use of total disc capacity, Level 3 and Level 5 combine striping with parity codes to allow recovery of data if a disc fails. Level 3 and Level 5 both use disc capacity more efficiently than Level 1.

Random Access Memory (RAM)
Memory where any location can read from or write to in random order, RAM usually refers to volatile memory where the contents are lost when power is removed. The user-addressable memory of a computer is random access memory.

Read Only Memory (ROM)
A chip that can be programmed once with bits of information. This chip retains the information even if the power is turned off. When the information is programmed into the ROM, it is called burning the ROM.

Rotational Speed
The speed at which the media spins, measured by revolutions per minute (RPM).

SCA (Single-Connector Attachment)
An interface connection that transfers power and data through the same connection. Used in applications such as RAID and with servers. 80pin

SCSI (small Computer Systems interface)
A high-speed interface standard to connect up to 7 devices on the same controller. Usually hard discs, tape drive and CD-ROM.

Sector
A section of track whose size is determined by formatting. When used as an address component, sector and location refer to the sequence number of the sector around the track.

Seek
The movement of the heads to a specified track address.

Seek time
Time required, on average, to move the data heads to another location (cylinder) on the discs.

Storage Capacity
The amount of data that can be stored in memory, specified in megabytes (Mbytes) or gigabytes (Gbytes).

Ultra ATA
Industry-accepted standard that allows a maximum data transfer rate of 33 Mbytes per second using an ATA (IDE) interface. Fully backward-compatible with earlier versions of ATA.

Ultra ATA/66
Industry-accepted standard that allows a maximum data transfer rate of 66 Mbytes Per second using an ATA (IDE) interface, Fully backward-compatible with earlier versions of ATA.

Ultra SCSI
Ultra SCSI is an evolution of the standard SCSI interface. Sometimes referred to as Fast 20, Ultra SCSI enables external transfer rates Of up to 20 Mbytes per second on an 8-bit bus and up to 40 Mbytes per second on a 16-bit bus. Ultra SCSI uses the same physical connections as SCSI-2 and is fully backward- compatible. To reach the maximum transfer rates of up to 20 (8-bit) or up to 40 (16-bit) Mbytes per second, both the controller and disc drive must be Ultra SCSI devices. Ultra SCSI also reduces total cable lengths to half of the Fast SCSI-2 specification.

Ultra 160 SCSI
Provides bus data rates of 160 Mbytes per second and easy integration of up to 16 devices on the SCSI bus using cable lengths up to 12 meters. Low Voltage Differential doubles SCSI bus rates and provides the integration flexibility and data integrity of High Voltage Differential at single-ended costs. Ultra 160 SCSI LVD is fully backward compatible to all previous single-ended versions of SCSI, taking advantage of the previously installed multi-billion dollar product base. When an Ultra]. Ultra 160 drive is installed on a previous version SCSI bus, performance will default to the specifications of that bus.

Ultra2 SCSI
Provides bus data rates of 80 Mbytes per second and easy integration of up to 16 devices on the SCSI bus using cable lengths up to 12 meters. Low Voltage Differential doubles SCSI bus rates and provides the integration flexibility and data integrity of High Voltage Differential at single-ended costs. Ultra2 SCSI LVD is fully backward-compatible to all previous single-ended versions of SCSI, taking advantage of the previously installed multi-billion dollar product base. When an Ultra2 drive is installed on a previous version SCSI bus, performance will default to the specifications of that bus.