Exabyte EXB-8505 8mm Owner's manual

510504-002
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Copyright
Copyright 1994 by Exabyte Corporation. All rights reserved. This
item and the information contained herein are the property of
Exabyte Corporation. No part of this document may be reproduced,
transmitted, transcribed, stored in a retrieval system, or translated
into any language or computer language in any form or by any
means, electronic, mechanical, magnetic, optical, chemical, manual,
or otherwise, without the express written permission of Exabyte
Corporation, 1685 38th Street, Boulder, Colorado 80301.
Disclaimer
Exabyte Corporation makes no representation or warranties with
respect to the contents of this document and specifically disclaims
any implied warranties of merchantability or fitness for any
particular purpose. Further, Exabyte Corporation reserves the right
to revise this publication without obligation to notify any person or
organization of such revision or changes.
Trademark Notices
EXABYTE is a registered trademark and EXATAPE and
Compression Integrity Check are trademarks of Exabyte
Corporation. All other brand and product names are trademarks or
registered trademarks of their respective companies.
Revision History
Revision Date
000 September 1992
001 March 1994 (preliminary draft for EXB-8205XL
and EXB-8505XL)
002 May 1994
Exabyte Corporation
1685 38th Street
Boulder, Colorado 80301
[phone]
510504-002
ii EXB-8205 and EXB-8505 510504
(Standard and XL)

Changes and Enhancements to This Manual
This revision (510504-002) of the EXB-8205 and EXB-8505 Product
Specification for Standard and eXtended Length (XL) Configurations
replaces the EXB-8205 8mm Cartridge Tape Subsystem Product
Specification (510703) and the EXB-8505 8mm Cartridge Tape Subsystem
Product Specification (510504). This manual includes the following
changes and enhancements:
The manual has been reorganized for easier reference. Chapters 1
through 3 include a general description of the tape drives, tape drive
functions, and related products; chapter 4 includes requirements for
installation, operation, and maintenance; chapter 5 includes SCSI
specifications; and chapters 6 and 7 include functional specifications and
compliance with safety and regulatory standards.
Information about the EXABYTE®EXB-8205 and EXB-8505 has been
consolidated into one manual. Information about the “eXtended Length”
(XL) configurations of these tape drives has also been included.
In the Related Products section, a description of the EXB-210 8mm
Library has been included. Information about extended length media,
including the Recognition System stripe on 160m XL EXATAPEädata
cartridges has been added. Exabyte cleaning cartridge information has
also been updated.
Detailed information about the relationship between physical track
structures and logical data formats has been added to the Physical
Format section.
May 1994 EXB-8205 and EXB-8505 iii
(Standard and XL)

Product Warranty Caution
The EXB-8205, EXB-8205XL, EXB-8505, and EXB-8505XL 8mm
Cartridge Tape Subsystems are warranted to be free from defects in
materials, parts, and workmanship and will conform to the current
product specification upon delivery. For the specific details of your
warranty, refer to your sales contract or contact the company from
which the tape drive was purchased.
The warranty for the EXB-8205, EXB-8205XL, EXB-8505, and
EXB-8505XL shall not apply to failures caused by:
Physical abuse or use not consistent with the operating instructions or
product specifications provided by Exabyte’s personnel or agent for the
applicable equipment.
Use of any type of cleaning material other than an EXABYTE 8mm
Cleaning Cartridge (or an Exabyte-approved cleaning cartridge).
Modifications by other than Exabyte’s personnel or agent in any way
other than those approved by Exabyte, provided the warranty shall not
be voided by the repair or replacement of parts or the attachment of
items in the manner described in maintenance or installation instructions
provided by Exabyte.
Repair by other than Exabyte’s personnel or agent in a manner contrary
to the maintenance instructions provided by Exabyte.
Removal of the Exabyte serial number tag.
Physical abuse due to improper packaging of returns.
CAUTION
Returning the EXB-8205, EXB-8205XL, EXB-8505, or EXB-8505XL in
unauthorized packaging may damage the unit and void the warranty.
If you are returning the tape drive for repair, package it in its original
packaging (or in replacement packaging obtained from your vendor).
Refer to the packing instructions in this manual.
If problems with the tape drive occur, contact your maintenance
organization; do not void the product warranty by allowing
untrained or unauthorized personnel to attempt repairs.
iv EXB-8205 and EXB-8505 510504
(Standard and XL)

Contents
About This Manual xii
IntendedAudience.......................................xii
HowThisManualisOrganized................................xii
RelatedPublications ..................................... xiii
ConventionsUsedinThisSpecification.......................... xiv
1Features 1-1
Features ........................................... 1-2
Read/Write Compatibility with Other Tape Drives . . . . . . . . . . . . . . . 1-4
DataCompression .................................. 1-6
CustomEEPROMOptions ............................. 1-7
StorageCapacity ................................... 1-8
PhysicalDescription ..................................... 1-9
FrontPanelControlsandIndicators........................ 1-9
BackPanelComponents...............................1-11
InternalComponentsoftheTapeDrive......................1-13
SizeandWeight....................................1-17
RelatedProducts .......................................1-18
IntegrationwithOtherExabyteProducts.....................1-18
EXATAPEÔDataCartridges ............................1-20
ExabyteCleaningCartridges ............................1-22
2Recording Format 2-1
Helical-ScanRecording ................................... 2-2
PhysicalFormat........................................ 2-3
PhysicalTrackStructure............................... 2-3
PhysicalBlocks .................................... 2-9
SearchFields .....................................2-10
ServoAreas ......................................2-10
Recording Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
LogicalFormat ........................................2-12
SupportedLogicalFormats .............................2-12
LogicalBlocks.....................................2-13
GapBytes .......................................2-15
GapBlocksandGapTracks.............................2-16
Filemarks .......................................2-17
Setmarks (EXB-8505 and EXB-8505XL only) . . . . . . . . . . . . . . . . . . . 2-18
EndofData(EOD)..................................2-18
TrackandBlockCounts ...................................2-19
May 1994 EXB-8205 and EXB-8505 v
(Standard and XL)

3Functional Description 3-1
WriteOperations ....................................... 3-2
DataFlowandDataCompression ......................... 3-2
StreamingandStart/StopModes.......................... 3-4
ThresholdsDuringaWriteOperation ....................... 3-5
Error Detection, Correction, and Recovery Procedures . . . . . . . . . . . . . 3-6
ReadOperations........................................ 3-7
ThresholdsDuringaReadOperation ....................... 3-8
4Requirements for Use 4-1
InstallationRequirements .................................. 4-2
RequirementsforSettingtheSCSIID........................ 4-2
RequirementsforMountingtheTapeDrive.................... 4-3
RequirementsforSCSIBusTermination...................... 4-6
RequirementsforConnectingaSCSICable.................... 4-7
Operation 4-11
Power-OnMode................................... 4-11
TapeDriveControls ................................ 4-11
DeviceStates..................................... 4-11
LoadingDataCartridges.............................. 4-14
UnloadingDataCartridges ............................ 4-15
ResettingtheTapeDrive.............................. 4-16
UsingSCSICommands............................... 4-17
PreventiveMaintenance .................................. 4-17
CleaningtheTapeDrive.............................. 4-17
DeterminingWhentheTapeDriveNeedsCleaning.............. 4-18
LoadingNewMicrocode.................................. 4-18
ShippingRequirements................................... 4-19
ShippingCartons .................................. 4-19
UnpackingandPackingInstructions....................... 4-20
5Interface Specifications 5-1
SCSIFeatures ......................................... 5-2
PhysicalPath ......................................... 5-2
SCSIMessages......................................... 5-3
SCSICommands........................................ 5-4
UsingSCSICommands.................................... 5-6
WritingData...................................... 5-6
ReadingData ..................................... 5-6
ErasingData...................................... 5-6
SearchingforData .................................. 5-7
CopyingMicrocode.................................. 5-7
InquiringAboutTapeDriveStatus......................... 5-7
PerformingDiagnosticTests............................. 5-8
SettingOperatingParameters............................ 5-8
vi EXB-8205 and EXB-8505 510504
(Standard and XL)

6Functional Specifications 6-1
PerformanceSpecifications ................................. 6-2
WriteAccessTime .................................. 6-2
ReadAccessTime................................... 6-2
TapeSpeed ...................................... 6-3
RepositionTime.................................... 6-4
DrumRotationPeriod................................ 6-5
TapeTensionReleaseandDrumMotionSuspension .............. 6-5
DataTransferRate .................................. 6-6
ReliabilitySpecifications................................... 6-7
ServiceLife ...................................... 6-7
Machine Reliability: Mean Time Between Failures (MTBF) . . . . . . . . . . . 6-7
DataIntegrity..................................... 6-9
DataReliability ....................................6-10
PowerSpecifications.....................................6-12
Voltages ........................................6-12
PowerConnector...................................6-13
Grounding Hole and Ground Tab . . . . . . . . . . . . . . . . . . . . . . . . . 6-14
EnvironmentalSpecifications................................6-15
OperatingEnvironment...............................6-16
AirFlowRequirements ...............................6-17
ParticulateContaminationLimits .........................6-17
ShockSpecifications .................................6-18
Vibration Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-19
AcousticNoise ....................................6-20
7Safety and Regulatory Agency Compliance 7-1
SafetyAgencyStandards .................................. 7-2
ElectrostaticDischarge(ESD)................................ 7-2
Electromagnetic Compatibility (EMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3
RadiatedSusceptibility.................................... 7-3
Glossary G-1
Index I-1
May 1994 EXB-8205 and EXB-8505 vii
(Standard and XL)

Figures
Features
Figure 1-1 Comparisonofthefourtapedrives...................... 1-3
Figure 1-2 Frontpanel.................................... 1-9
Figure 1-3 Labellocationandcontent .......................... 1-10
Figure 1-4 Backpanel(single-endedconfiguration).................. 1-11
Figure 1-5 Internal components (EXB-8505 shown) . . . . . . . . . . . . . . . . . . 1-13
Figure 1-6 Locationofthereadheadsandwriteheads ................ 1-14
Figure 1-7 External dimensions in inches (and millimeters) . . . . . . . . . . . . . 1-17
Figure 1-8 EXB-210 8mm Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-18
Figure 1-9 Mini Tabletop CTSs with EXB-8505s installed . . . . . . . . . . . . . . . 1-19
Recording Format
Figure 2-1 Helical-scanrecording ............................. 2-2
Figure 2-2 Relationship of 8mm physical track structures to logical data formats . . 2-4
Figure 2-3 Physical track structure for 8500 and 8500c format . . . . . . . . . . . . . 2-5
Figure 2-4 Position of the tape drive’s heads relative to the tracks
(8500/8500c format) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
Figure 2-5 Physical track structure for 8200c track format . . . . . . . . . . . . . . . 2-7
Figure 2-6 Physical track structure for 8200 track format . . . . . . . . . . . . . . . . 2-7
Figure 2-7 Position of the tape drive’s heads relative to the tracks
(8200c format) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Figure 2-8 Physical block format for all logical formats
(8200c or 8500/8500c physical track structure shown) . . . . . . . . . . . 2-9
Figure 2-9 Logicalblockpacking(onephysicalblock) ................ 2-14
Figure 2-10 Gapbytes(onephysicalblock)....................... 2-15
Figure 2-11 One gap block and one gap track in two physical tracks . . . . . . . . 2-16
Functional Description
Figure 3-1 Dataflowduringawriteoperation...................... 3-2
Figure 3-2 Dataflowduringareadoperation ...................... 3-7
Requirements for Use
Figure 4-1 SCSI ID jumper block on the back panel (single-ended configuration) . . 4-2
Figure 4-2 Mountingholesonthesides.......................... 4-4
Figure 4-3 Mountingholesonthebottom......................... 4-4
Figure 4-4 Mounting hole dimensions in inches (and millimeters) . . . . . . . . . . 4-5
Figure 4-5 SCSIconnectorlocationonthebackpanel.................. 4-8
Figure 4-6 LEDs on the faceplate of the EXB-8505 and EXB-8505XL . . . . . . . . . 4-12
Figure 4-7 LEDs on the faceplate of the EXB-8205 and EXB-8205XL . . . . . . . . . 4-12
viii EXB-8205 and EXB-8505 510504
(Standard and XL)

Functional Specifications
Figure 6-1 Powerconnectorlocationonthebackpanel.................6-13
Figure 6-2 Chassisgroundlocationonbackpanel....................6-14
Figure 6-3 Temperatureandhumidityrangesforoperation..............6-16
Figure 6-4 Particulatecontaminationspecificationvs.typicaloffice .........6-18
May 1994 EXB-8205 and EXB-8505 ix
(Standard and XL)

Tables
Features
Table 1-1 Comparisonoftapedrivefeatures....................... 1-4
Table 1-2 Read/write compatibility of Exabyte 8mm tape drives . . . . . . . . . . . 1-5
Table 1-3 Dataformatfeatures............................... 1-5
Table 1-4 Approximate capacities of EXATAPE data cartridges . . . . . . . . . . . . 1-8
Table 1-5 EXATAPE media compatibility with 8mm tape drives . . . . . . . . . . 1-21
Recording Format
Table 2-1 Recording parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
Table 2-2 Typeandsizeoffilemarksforeachformat ................. 2-17
Table 2-3 Track and physical block counts for 8200 and 8200c formats . . . . . . . 2-20
Table 2-4 Track and physical block counts for 8500 and 8500c formats . . . . . . . 2-20
Requirements for Use
Table 4-1 Connector pin assignments for differential tape drives . . . . . . . . . . . 4-9
Table 4-2 Connector pin assignments for single-ended tape drives . . . . . . . . . 4-10
Table 4-3 LEDstatesduringoperation ......................... 4-13
Table 4-4 Single pack and multi-pack shipping dimensions and weights . . . . . 4-19
Interface Specifications
Table 5-1 SCSImessages .................................. 5-3
Table 5-2 SCSI-2commandset............................... 5-4
Functional Specifications
Table 6-1 Nominaltapespeed ............................... 6-3
Table 6-2 File-searchtapespeeds.............................. 6-3
Table 6-3 Typicalrewindtimes............................... 6-4
Table 6-4 Drumrotationperiods.............................. 6-5
Table 6-5 Datatransferrates ................................ 6-6
Table 6-6 Powerspecificationsforstandardvoltages................. 6-12
Table 6-7 Powerconnectorpinassignments ...................... 6-13
Table 6-8 Environmentalspecifications......................... 6-15
Table 6-9 Temperatureandhumidityspecifications.................. 6-16
Table 6-10 Particlecontaminationlimits ........................ 6-17
Table 6-11 Shockspecifications.............................. 6-18
Table 6-12 Vibration specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-19
Table 6-13 Acousticnoiselimits ............................. 6-20
xEXB-8205 and EXB-8505 510504
(Standard and XL)

About This Manual
This product specification describes the functional, performance, and
environmental specifications for the following EXABYTE®8mm
Cartridge Tape Subsystems (tape drives):
EXB-8205
EXB-8205XL (extended length)
EXB-8505
EXB-8505XL (extended length)
Intended Audience
This manual is for engineering, purchasing, or marketing personnel
who want to evaluate the EXB-8205, EXB-8205XL, EXB-8505, and
EXB-8505XL to determine the feasibility of integrating them into
product lines.
How This Manual is Organized
This manual contains the following chapters:
Chapter 1 describes the features of the tape drives, including
compatibility with other Exabyte 8mm Cartridge Tape
Subsystems, data compression, tape capacity, and custom
EEPROM options. This chapter also describes the physical
features of the tape drives, including mechanical and electrical
components.
Chapter 2 describes the physical and logical recording formats
used by the tape drives, including the implementation of
helical-scan recording technology.
Chapter 3 describes the functional features of the tape drives,
including how they perform read and write operations.
Chapter 4 lists the requirements for installing, operating,
maintaining, and shipping the tape drives.
Chapter 5 describes how the tape drives implement the Small
Computer System Interface (SCSI), including an overview of SCSI
messages and commands.
Chapter 6 lists performance, reliability, power, and environmental
specifications.
May 1994 EXB-8205 and EXB-8505 xi
(Standard and XL)

Chapter 7 describes compliance with regulatory and safety
agency standards, including electromagnetic susceptibility (EMI),
susceptibility to electrostatic discharge (ESD), and radiated
susceptibility.
This product specification contains a glossary and an index.
Related Publications
The following publications list additional, related information.
EXB-8205 and EXB-8505 8mm Cartridge Tape Subsystems
For information about installing, operating, and maintaining the
EXB-8205, EXB-8205XL, EXB-8505, and EXB-8505XL, and for
information about implementing SCSI commands, refer to the
following publications:
EXB-8205 and EXB-8505 8mm Cartridge Tape Subsystems SCSI
Reference for Standard and eXtended Length Configurations,
510503
EXB-8205 and EXB-8505 8mm Cartridge Tape Subsystems
Integration and Optimization for Standard and eXtended Length
Configurations, 510505
EXB-8205 and EXB-8505 8mm Cartridge Tape Subsystems
Installation and Operation for Standard and eXtended Length
Configurations, 302967
Libraries and Enclosures
For information about libraries and enclosures currently available for
the EXB-8205, EXB-8205XL, EXB-8505, and EXB-8505XL, refer to the
following publications:
EXB-210 8mm Library Product Specification, 510807
Mini Tabletop 8mm Cartridge Tape Subsystem Product
Specification, 520154
xii EXB-8205 and EXB-8505 510504
(Standard and XL)

Standards
For information about the standards used for the tape drives, refer to
the following publications:
ANSI Small Computer System Interface (SCSI), X3.131 - 1989
ANSI Small Computer System Interface-2 (SCSI-2), X3.131 -1994
ANSI/ISO/IEC 11319-1992 and ECMA-145, Information
Technology —8mm Wide Magnetic Tape Cartridge for
Information Interchange, July 1992
ISO/IEC 12246 and ECMA-169, Information Technology—8mm
Wide Magnetic Tape Cartridge Dual Azimuth Format for
Information Interchange, Helical Scan Recording
Conventions Used in This Specification
This specification uses special conventions to highlight notes, important
information, and cautions. These conventions are explained below.
Note: Read Notes for hints or suggestions about the topic or procedure
being discussed.
#Important Read
Important text to learn crucial information about the
topic or procedure being discussed.
CAUTION
Read the information in CAUTION boxes to learn ways to avoid
damaging the equipment.
May 1994 EXB-8205 and EXB-8505 xiii
(Standard and XL)

Notes:
xiv EXB-8205 and EXB-8505 510504
(Standard and XL)

1
Features
This chapter provides an overview of the EXB-8205, EXB-8205XL,
EXB-8505, and EXB-8505XL, including:
Features
Physical description
Related products
May 1994 EXB-8205 and EXB-8505 1-1
(Standard and XL)

Features
The EXB-8205, EXB-8205XL, EXB-8505, and EXB-8505XL are enhanced
8mm digital helical-scan cartridge tape subsystems (tape drives). The
tape drives are packaged in the industry standard 5.25-inch half-high
form factor, which allows for ease of integration across a multitude of
platforms.
Featuring an integral Small Computer System Interface (SCSI)
controller (either single-ended or differential configuration), these
tape drives are the easily integrated solution to your journaling,
archiving, data interchange, software distribution, imaging, data
acquisition, and backup/restore needs.
Note: This specification applies to the EXB-8205, EXB-8205XL,
EXB-8505, and EXB-8505XL. However, most of the
illustrations in this manual show the EXB-8505.
In their compressed modes, the EXB-8205 can store up to 5 GBytes
and the EXB-8505 can store up to 10 GBytes on a single 112m data
cartridge, assuming an average compression ratio of 2:1.
The eXtended-Length (XL) configurations of these tape drives
provide additional capacity by supporting EXATAPE160m XL 8mm
Data Cartridges. Assuming an average compression ratio of 2:1, the
EXB-8505XL can store up to 14 GBytes of data on a single 160m XL
data cartridge. Assuming the same compression ratio, the
EXB-8205XL can store up to 7 GBytes on a single data cartridge.
For more information on EXATAPE data cartridge capacity, see
page 1-8. For more information on EXATAPE data cartridges, see
page 1-20.
#Important EXATAPE 160m XL 8mm Data Cartridges are only
supported by the extended length tape drives (EXB-8205XL and
EXB-8505XL). The standard tape drives (EXB-8205 and
EXB-8505) cannot write on or read from 160m XL data cartridges
and will automatically eject them.
AsshowninFigure1-1,thefourtapedrivemodelslookidentical,
except for minor differences in the LEDs and the unload button.
1-2 EXB-8205 and EXB-8505 510504
(Standard and XL)
1Features

The EXB-8205XL and EXB-8505XL are fully compatible with the
EXB-8205 and EXB-8505; each extended length tape drive supports all
of the tape sizes and data formats supported by the corresponding
standard tape drive. You can distinguish an extended length tape
drive from a standard tape drive by checking the unload button. The
extended length tape drives have a raised diamond pattern on the
unload button.
Table 1-1 compares the features of the tape drives.
Figure 1-1 Comparison of the four tape drives
May 1994 EXB-8205 and EXB-8505 1-3
(Standard and XL)
1Features

EXB-8505 and EXB-8505XL EXB-8205 and EXB-8205XL
Form factor Half-high 5.25 inches
Data formats supported 8200, 8200c, 8500, 8500c 8200, 8200c
Buffer size 1.0 MByte
Data transfer rate* 1.0 MByte per second 500 KBytes per second
Search speed 75X normal (8500c, 8500, and 8200c formats)
10X normal (8200 format)
75X normal (8200c format)
10X normal (8200 format)
Synchronous data transfer yes
Time-to-clean LED indication yes
Compression yes
*These figures represent the maximum sustained data transfer rate, assuming a 2:1 data compression ratio.
Read/Write Compatibility with Other Tape Drives
The EXB-8205, EXB-8205XL, EXB-8505, and EXB-8505XL can read data
cartridges written by other Exabyte 8mm tape drives, including the
EXB-8200, the EXB-8200SX, the EXB-8500, and the EXB-8500c. They
can also write on data cartridges that are intended for use with these
other tape drives.
Supported Formats
The EXB-8505 and EXB-8505XL read and write data in four logical
formats:
8200
8200c (compressed)
8500
8500c (compressed)
The EXB-8205 and EXB-8205XL read and write data in two logical
formats:
8200
8200c (compressed)
Table 1-2 shows the read and write compatibility of the four logical
data formats with the tape drives. Table 1-3 compares these data
formats.
Table 1-1 Comparison of tape drive features
1-4 EXB-8205 and EXB-8505 510504
(Standard and XL)
1Features

Atape
written in
this format...
Can be read and written by an ...
EXB-8205 EXB-8205 XL EXB-8505 EXB-8505 XL
8200 4444
8200c 4444
8500 44
8500c 44
8200
format 8200c format*
8500 format
(EXB-8505 and
EXB-8505XL)
8500c format*
(EXB-8505 and
EXB-8505XL)
Maximum sustained
data transfer rate 262
KBytes/sec 500 KBytes/sec 1.0 MByte/sec
Maximum capacity on
112m tape 2.5
GBytes 5.0 GBytes 10.0 GBytes
Maximum capacity
on 160m XL tape (XL
configurations only)
3.5
GBytes 7.0 GBytes 14.0 GBytes
Track
structure
Helical scan: One write head writes
a single data track
witha–10°azimuth.
Helical scan: Two write heads write
two overlapping data tracks.
Track 1 = +20°azimuth.
Track 2 = –10°azimuth.
Supports partitions no yes
Supports setmarks no yes
Long filemarks 270 tracks (2,160 KBytes) 6 tracks (48 KBytes)
Short filemarks 23 tracks
(184 KBytes) one 1-KByte physical block
Setmarks no yes–6 tracks
(48 KBytes)
EOD mark no yes–849 tracks yes–602 tracks
Search fields no yes
Logical
block packing no yes
*Assumes a data compression ratio of 2:1.
Table 1-2 Read/write compatibility of Exabyte 8mm tape drives
Table 1-3 Data format features
May 1994 EXB-8205 and EXB-8505 1-5
(Standard and XL)
1Features

Determining the Tape Format
When writing data to tape, the tape drive does one of the following:
If the tape is positioned at the logical beginning of tape (LBOT),
the tape drive writes data in the default format or whatever
format you select with the SCSI MODE SELECT (15h) command.
(The tape drive allows only one format on any one tape.)
If the tape is positioned at any other valid position for writing
data, the tape drive writes data in the same format as the data
already on the tape.
When reading a data cartridge, the tape drive automatically
determines the tape’s format.
Data Compression
When the tape drive compresses data, it uses the established
Improved Data Recording Capability (IDRC) algorithm. Licensed
from IBM, this algorithm is the de facto standard in mainframe
environments. The tape drives also use the Exabyte Compression
Integrity Check™ feature to ensure that data is accurately compressed
and decompressed into the original form sent by the initiator.
The compression algorithm is completely contained in an Exabyte
proprietary integrated circuit. The tape drive invokes the compression
algorithm intelligently, constantly monitoring the compression ratio
to determine whether compressing the data will actually decrease the
size of the data set. The tape drive sends compressed data to tape only
when it benefits the user’s storage capacity and throughput.
Although the actual data compression ratio depends on the type of
data, the EXB-8205, EXB-8205XL, EXB-8505, and EXB-8505XL achieve
an average compression ratio of 2:1.
For detailed information about how the tape drives compress data,
see Chapter 3.
1-6 EXB-8205 and EXB-8505 510504
(Standard and XL)
1Features