Quantum LTO-2 manual Data Compression, Servo-tracking, Faults, Tracking is re-established

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Chapter 4 Theory

Data Compression

• For two or more known C1 codeword pairs in error, the matrix is

 

 

computed by firmware and the correction is performed by hardware.

 

 

• For one or more unknown C1 codeword pairs, syndromes are

 

 

generated by hardware, error location is computed by firmware, the

 

 

matrix is computed by firmware and the correction is performed by

 

 

hardware.

 

During a write operation, if the servo system detects an error that may

 

Servo-tracking

Faults

result in adjacent data tracks being over-written, the write operation is

 

 

aborted. The write operation will not continue until the correct servo

 

 

tracking is re-established.

Data Compression

Typical data streams of text, graphics, software code, or other forms of data contain repeated information of some sort, whether it is at the text level where you can readily recognize regular repetitions of a single word, or at the binary level where the repetitions are in bits or bytes. Although most data is unique and random, the binary level data exhibits patterns of various sizes that repeat with varying degrees of regularity.

Storage efficiency is increased if the redundancies or repetition in the data are removed before the data is recorded to tape. Data compression technology significantly reduces or eliminates redundancies in data before recording the information to tape. This increases the amount of data that can be stored on a finite medium and increases the overall storage efficiency of the system.

With data compression, the redundant information in a data stream is identified and represented by codewords or symbols, which allow the same data to be recorded in a fewer number of bits. These codewords or symbols point back to the original data string, using fewer characters to represent the strings. Because these smaller symbols are substituted for the longer strings of data, more data can be stored in the same physical space.

Some important benefits result from data compression in tape drives:

LTO-2 Half-Height Tape Drive User’s Guide

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Contents 72 Copyright Statement Contents Chapter Operation Safety Compliance EMC Compliance Injected Noise ReliabilityMean Time to Replace Chapter Troubleshooting Guide Figures Figures Viii Tables Tables Audience Purpose Document Organization PrefaceNotational ConventionsTech Tip Related SCSI-2 SpecificationDocuments ContactsSend faxes for the Customer Support Department to Customer SupportSend e-mail for the Customer Support Department to Visit our web site1Introduction Features 2Installation and Quick Start Quick Start Guide Internal LTO-2 Half-Height TapeDrive Quick Start Desktop LTO-2 Internal Tape Drive Guidelines and Cautions Unpacking and InspectionInstalling an Internal LTO-2 Half-Height Tape Drive Drive Installation InstructionsScsi ID Jumper PinsScsi ID=8 Open Shunted Default Terminator PowerJumpers Mounting Horizontally or vertically see figureWithin 5 degrees of horizontal Internal LTO Half-Height Tape Drive Mounting Dimensions Rear View Internal LTO-2 Half-Height Tape Drive Checking the Scsi Termination Connecting aSerial Cable for Tape LibrariesInstalling the LTO Driver Connecting a PowerPin Numbers Description CableInstalling a Desktop LTO-2 Half-Height Tape Drive Desktop LTO-2 Half-Height Tape Drive CordLTO-2 Half-Height Tape Drive User’s Guide 3Operation Generic Front Panel Display Understanding the Front Panel DisplayEOT Blink CodesLoading a Cartridge Unloading a Cartridge Using LTO CartridgesWrite-protecting a CartridgeCartridge Care MaintenanceRetensioning the Tape Drive MaintenanceOperation Drive Maintenance Operation Drive Maintenance Track Layout 4TheoryShows the layout of data on an LTO tape Recording Method Data BufferData Integrity C1 ECC Data Compression FaultsServo-tracking Tracking is re-establishedData Compression Considerations Compression Intelligent DataPage 5Specifications Internal Scsi Drive Specification Without Bezel With Bezel Physical SpecificationsInternal LTO-2 Half-Height Tape Drive Dimensions Power Specifications Specification +12 VDC + 5VDCIdle Power Watts RMS Standby Power Typical Operating Power Specification LTO-2 Drive Performance SpecificationsSpecification Value Environmental Requirements Specification Operational Non-operationalReliability Injected NoiseAt any frequency between 45 Hz and 20 MHz Mean Time Between Failures Specification DescriptionMean Time to LTO Cartridge SpecificationsReplace Environmental ConsiderationsRegulatory Compliance Cartridge MemoryReliability Country Regulatory Organization Compliant to EMC Compliance Country Regulatory Organization Compliant to Disposal of Electrical and Electronic Equipment 6UNIX Settings Word About Scsi Controllers Configuring for the DEC/Compaq Unix EnvironmentParameters Save the file. Then run the following commandTargets Finding CurrentTypes ControllersConfiguring Device FileSt.conf Smit Set the Block size to Enter Smit at the Tape Drive menu by typing smit tapeUsing the command Configuring for SCO Open ServerThis command produces output similar to Current tape drives can be found using the commandConfiguring the LTO-2 Half-Height Tape Drive with mkdev Finding Existing Scsi Controllers Devices Configuring for LinuxTo find existing Scsi devices execute the command You may see output similar toYou should see output similar to Configuring for SGI Irix Scsi controllers and devices use the commandOutput of the command will be similar to the following Configuring for HP-UX ConfigurationHardware/Driver Unix Settings Configuring for HP-UX Installation Best Practices 7Troubleshooting GuideClicking on Computer Management Device Manager Troubleshooting Suggestions Troubleshooting Guide Troubleshooting Suggestions Red Hat Linux Windows Operating SystemTape will not Load into Tape Drive Problems with Tape Drive and CartridgeTape will not Eject from the Drive LTO-2 Half-Height Tape Drive User’s Guide Problems During Backup/Restore Operations Emergency Reset and Emergency Cartridge EjectPreviously Written Data on the Tape will be Destroyed If either of the following messages appears Tape is Write Protected Miscellaneous TapeAlert MessagesLTO-2 Half-Height Tape Drive User’s Guide Slow Backups LTO-2 Half-Height Tape Drive User’s Guide Index Index Scsi ID Tape drive