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A
Algorithm:
A programming term referring to the code generated for a particular mathematical
calculation or function.
ASPI:
“Advanced SCSI programming
Interface”. A standard SCSI
software interface that acts as a communication link between a host adapter
board and SCSI device drivers. ASPI
enables host adapters and device drivers to share a single SCSI hardware
interface.
ASPI Manager:
A software module that provides an
interface between ASPI modules, a host adapter board, and the SCSI devices
connected to the adapter. ASPI managers are written for a specific operating system
(such as NT or OS/2) and a specific family of host adapter boards.
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B
BUS:
A pathway for data transfer in a computer system.
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C
Cache: In the context
of the InveStore storage management software, the term
“cache” has more than one meaning.
The
first "cache" definition refers to files stored on the NT optical server hard drive that are used to
track and access optical and CD media in the storage library. These
cache files contain the directory tree information for each optical disk in the
system and are used to speed
access to the data
stored on the optical disk.. They do not contain
the actual data -- all data resides safely on optical media.
The second "cache"
definition refers to a level of memory (RAM) cache used in the Pegasus InveStore
HCM layer. This cache is used as a temporary area through which writes
pass on their way to optical as well as a place to maintain recently used files
for speedy ready access. See The
InveStore RAM Cache Algorithm for more details.
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D
DASD: “Direct Access Storage Device”.
This refers to the magnetic hard drive that the NT operating system, and
InveStore is installed on. It is
also the space used by NT for its PAGEFILE requirements.
Differential
SCSI: Differential signals
occupy two conductors with a positive (+) and negative (-) polarity component of
the signal. This minimizes signal noise and allows the SCSI bus to operate
reliably over greater distances at a higher speed.
This specification supports a total bus length of up to 25 meters for
both 2.6 GB and 5.2GB drives.
Drives:
a device that can read or write to removable media such as an optical disk or
CD. A library has at least one drive.
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E
Eject
— When a jukebox opens the mail slot and places a volume to be removed in the
slot. Unmounting a volume causes the optical disk
containing the volume to be ejected.
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F
Fiber
Channel - a highly-reliable, gigabit interconnect technology (using either
optical or a copper cable) allows concurrent communications among workstations,
mainframes, servers, data storage systems, and other peripherals using SCSI and
IP protocols. It provides interconnect systems for multiple topologies that can
scale to a total system bandwidth on the order of a terabit per second.
Format:
(aka initialize) Preparing an optical disk for use.
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G
H
Host
Adapter board: A
printed circuit board that installs in a standard computer and provides a SCSI
bus connection so that SCSI devices can be connected to the computer.
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I
I/O: “Input/output” system on a PC
system motherboard. Refers to an operations, program, or device whose purpose is to enter
data into or to extract data from a computer.
This involves the communication on the motherboard bus to the
various devices used in this data processing and storage.
Initialize:
This refers to the formatting of the optical media, preparing it with the
InveStore file system and making it ready to receive data.
IRQ: “Interrupt
Request Channel”. A “request
channel” by which a device on the system motherboard, receives access to the
CPU.
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J
Jukebox:
A device that uses robotics to move optical media from internal storage slots to
internal optical drives for the purpose of “Read” and “Write”
operations. It is commonly referred
to as an optical library, since it contains media with data.
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K
L
Lazy
Write:
InveStore write mode under which data written to the optical disk is first
stored in a RAM cache and written to optical at a later time.
Library:
This refers to the individual standalone optical drive or jukebox.
Each library can contain at least on volume or piece of media.
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M
Mailslot:
a port on the jukebox hardware through which individual media can be imported or
ejected.
Magneto
Optical: Optical storage technology that uses a laser to change the
properties of the storage disk surface magnetically. Users can read,
write, erase, etc. just as they would with a hard disk, but the data is more
stable. Depending on the software utilized to control the drive, as you need
space on a platter you can delete files (unlike WORM).
Media:
refers to the individual optical disk cartridge where the data is stored.
Mount:
Adding a volume to a library. Under Pegasus InveStore mounting involves
importing and reading a disk in order to makes it available to the
operating system.
Multitasking:
The execution of commands in such a way that more than one command is in
progress at the same time.
Multithreading:
A situation in which a host adapter has more than one outstanding command to two
or more SCSI devices.
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N
O
Optical
device:
This refers to an optical, CD, or DVD jukebox, changer or standalone optical drive.
Optical
disk — A cartridge-like device on
which data is stored and retrieved by an optical disk drive.
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P
PORT
I/O Address: A
window through which software programs communicate commands to an installed host
adapter board on the system motherboard.
Picker:
The
part of the jukebox robotics responsible for moving a disk from a storage slot
to a drive and back again. Some jukeboxes feature "dual pickers"
which allows two disks to be swapped without the need to return a disk back to a
storage slot first.
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Q
R
S
SCSI:
“Small Computer System Interface”. An
interface standard that defines physical and electrical connections for devices.
SCSI provides a standard interface that enables many different kinds of
devices, such as disk drives, magneto optical disks, CD-ROM drives, and tape
drives to interface with the host computer.
SCSI Device:
A device such as a host adapter board,
fixed disk drive or CD-ROM drive that conforms to the SCSI interface standard
and is attached to a SCSI bus cable.
Single-ended
SCSI: For each signal that
needs to be sent across the bus, there exists a wire to carry it.
This specification supports a total Bus length of up to 6 meters for
2.6GB devices, and 3 meters for 5.2GB devices.
Slots:
Storage locations with a jukebox or changer. For example, an MO jukebox
has one slot for each optical disk that it can hold. A standalone drive
has no slots. Pegasus InveStore software licenses are sold with
various slot "capacities" that correspond to the capacities of
hardware available on the market.
Standalone
drive — An optical disk drive that is not in a jukebox. Optical disks are
manually inserted in the drive.
Sub-system:
Refers to the optical server hardware including the PC,
motherboard, SCSI adapter card, SCSI cable, terminator, and storage device.
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T
Termination:
A physical
requirement of the SCSI bus. The first and last devices on the SCSI bus must
have terminating resistors installed (or a terminator plug), and the devices in
the middle of the bus must have terminating resistors removed.
Poor termination can cause
“reflections” when transfer rates increase and/or more devices are added on
the Bus. This can lead to data transfer errors.
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U
UDF:
Universal Disk Format - a file system defined by OSTA.
UDF is intended to enable file interchange among different operating systems.
Unmount:
Removing a volume (disk) from a library.
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V
VIM:
Volume Interface Manager = The InveStore programmer's API consisting of a
group of C function calls contained within a DLL that provide access to the
storage functionality of the InveStore kernel.
Virgin
disk:
An optical disk that has not been formatted with a file system.
Volume:
The name used to refer to a media cartridge and more specifically a single side of an optical disk.
Each side of each disk is treated as a discreet volume, and requires a
unique name. These volumes appear
and are accessed as the first level sub-directory at the root of the assigned
drive letter. All data is contained
within the directory tree structure of these volumes.
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W
WORM:
Write-Once-Read-Many
technology used in many applications for because of the integrity of the data
and the accepted legal admissibility of files stored using the technology. In
the case of “Ablative" or "True" WORM, data written to a disk
is actually etched into the surface of the platter creating a permanent record.
Another form, CCW WORM is based on Magneto/Optical technology.
CCW achieves the WORM characteristic through special MO media that
signals the optical drive not to rewrite media sectors.
An advantage of CCW media is that it conforms to ISO standards, allowing
it to be read with drives from any manufacturer adhering to the standard. WORM
records are unalterable with the exception of destroying the platter. Legal
documents, research information, historical records, etc., are all examples of
information that require permanent storage.
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X
Y
Z
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