Click Here!
home account info subscribe login search My ITKnowledge FAQ/help site map contact us


 
Brief Full
 Advanced
      Search
 Search Tips
To access the contents, click the chapter and section titles.

Complete Idiot's Guide to Linux
(Publisher: Macmillan Computer Publishing)
Author(s): Manuel Ricart
ISBN: 078971826x
Publication Date: 12/22/98

Bookmark It

Search this book:
 
Previous Table of Contents Next


Backup Media

There is an incredible array of choices for backup media these days:

  Floppy disks
  Floptical disks
  Magneto-optical (MO) disks
  Quarter-inch cartridge tapes (QIC)
  Minicartridge QIC and Travan tapes
  Write-once CD-ROMs (CD-Rs)
  Rewritable CD-ROMs (CD-RWs)
  Iomega Jaz and Zip drives
  Nine-track magnetic tapes
  4mm Digital Audio Tapes (DATs)
  8mm cartridge tapes
  DLT cartridge tapes

These media are described in the following sections.

Floppy Disks

Floppy disks are the most convenient backup medium available because your system likely has a built-in floppy disk drive. The standard capacity is 1.44MB. Some 2.88MB drives made it into the market a few years back, but they never caught on. The drawback of floppy disks is that they are slow, fairly expensive (about 30–60 cents per disk), and not very useful for backing up anything that requires more than a couple of disks. The one advantage is that most computers are equipped with one.

Floptical Disks

These higher-capacity disks take advantage of optical tracking technology to improve head positioning and therefore maximize the amount of data that can be packed onto the surface of a disk. Floptical drives can read standard 1.44MB and 720KB floppy disks. Density of information can be anywhere from a few megabytes to 200MB per disk.

Magneto-Optical Disks

Magneto-optical disks have a plastic or glass substrate coated with a compound that, when heated, allows a magnetic source to realign the polarity of the material. When the material cools, its polarity is frozen. The material can be rewritten by a subsequent write operation.

Data is read by a lower-intensity beam, and the polarization pattern is interpreted as a byte stream. A wide variety of these devices are commercially available, ranging in format from 5 1/2 inches to 3 1/2 inches. These devices can store information ranging in size from 128MB to more than 2GB.

Read speed on MO disks is as fast as that on a hard disk. Write operations usually take a little longer but are still faster than write operations on a slow hard disk or a standard floppy disk. Medium reliability is very high.

Quarter-Inch Cartridge Tapes

QIC tapes get their name from the fact that the tape’s width is 0.25, or one quarter, of an inch. Many PC users are familiar with minicartridge QIC drives, but these are discussed in the next session, alongside Travan tapes.

QIC drives originally shipped as standard equipment on a number of older UNIX workstations and were the primary means for booting an “empty” system and for data interchange. The original QIC drives stored very small amounts (20-60 megabytes), but QIC-SCSI drives in the range of 250MB-525MB are currently popular. The largest QIC-SCSI drives shipping at the moment store 26GB (gigabytes) and store data at around 60MB per minute.

True QIC drives are exceedingly reliable and are favorites of many UNIX workstation users. The cartridges themselves are built like (heavy) tanks and can be read thousands of times.

Travan Tapes

A minicartridge QIC tape is a low-end, PC-market backup storage solution that uses the same .25-inch tape width found in true QIC drives. Some vendors are pushing the minicartridge format to store up to 1600MB by using a .315-inch format, resulting in Travan tapes.

Standard QIC tapes can hold anywhere from 11MB to 150MB and are usually designated as QIC-11 or QIC-24, depending on the amount of storage space they provide. Storage space in megabytes is indicated by the number following the QIC portion of the designation.

Sometimes tapes created on one vendor’s drive are not readable by another vendor’s drive. This is due to byte ordering and other special formatting issues. Within a vendor, tapes are usually backward compatible, meaning that you might be able to read lower-density tapes on a higher-density drive; however, you should verify this before you upgrade to a new drive in the same product line and discard your old one.

Travan tapes are similar in size to minicartridge QIC tapes but store 120–8000MB per tape depending on the type of tape drive mechanism used. Travan tapes are compatible with the minicartridge QIC tape formats, making them attractive if you have legacy minicartridge QIC tapes. Its price, capacity, and performance make this system a very attractive option.


Previous Table of Contents Next


Products |  Contact Us |  About Us |  Privacy  |  Ad Info  |  Home

Use of this site is subject to certain Terms & Conditions, Copyright © 1996-2000 EarthWeb Inc.
All rights reserved. Reproduction whole or in part in any form or medium without express written permission of EarthWeb is prohibited. Read EarthWeb's privacy statement.