文档介绍：Offline Data Management
Chapter 2 - Introduction
Define archiving
Discuss some of the issues affecting data storage
Define storage methods and terms
Highlight the need and examples of automated storage devices
Archiving
The long term storage of information externally to the puter system
Reduce amount of on-line storage required, but still store historic information
Paper records
Space consuming, difficult to index
Microfiche
Expensive to create
Tapes
Cheap media, slow sequential access
Optical media
Low cost, robust media, good random access
Data Storage Requirements
A4 page of text (unformatted) 2Kbytes
A4 B/W scanned drawing 50Kbytes
A5 24-bit scanned colour image 40Mbytes
***JB*** Example
Requirement will determine most applicable storage device
Need to plan for future requirements
NEAR-LINE
FAR-LINE
OFF-LINE
ON-LINE
Film - Paper - Archive
RAM
Fixed
Disk
ic
Removable
(mounted)
Optical
Removable
(mounted)
Tape (mounted)
Jukebox Media
(unmounted)
Automated Tape
(unmounted)
Shelved Jukebox Media
Shelved MO Media
Shelved Tape
FAST
HIGH
SLOW
LOW
LOW
SPEED
HIGH
COST
CAPACITY
Data Storage Defined
Automation
"Automation is the process, whereby electro-mechanical systems are added to a device to enable it to operate with the minimum of human intervention”
+
+
+
Device + Robotics
Need For Automation
Individual media items do not have sufficient capacity
Retrieval delayed by manual handling
User interaction may lead to errors
Requirement for "lights out" operation
Need to restore from multiple backups
Duplication of multiple tapes for off-site storage
Automated Storage Devices
Autoloaders
DAT/DLT
Single drive + multiple tapes
Libraries
DLT
Multiple drive capability + multiple slots
Optical jukeboxes
CD/MO
Multiple drive capability + multiple slots
Optical towers
CD/MO
Multiple drives
Chapter 3 - Technologies
Examine the various technologies available
Tape
Optical
Discuss media life issues
Tape Technologies (Se