As disk drives get larger and larger, answers to the questions of how to back up the data on them, and how to access that backed-up data when you need it, become more complex. Consequently, each backup option serves a different purpose and exacts a different price. There really isn't a simple solution. In some situations, you actually need to use a combination of backup schemes. The information that follows summarizes your choices.
Tape Cartridges
The most traditional backup medium, magnetic tape is still important in a lot of situations. Tape-drive makers have tried to keep pa
ce with the expanding disk capacities of our computers, and the latest inexpensive tape backup units, such as Hewlett-Packard's Colorado 5 GB and Iomega's DittoMax and DittoMax Pro, are eminently affordable. With per-cartridge capacities between 3 and 10 GB, media costs in the $25 to $40 range, and drives selling for $200 to $300, tape is a quick, readily available alternative that's well suited to individual users and small servers. More expensive, server-oriented tape backup units can store 20 to 40 GB per cartridge, with greater reliability and concomitant greater cost.
Optical Disks
Optical disk backup has a lot going for it: permanence, random-access restores, and inexpensive media. But the need for streaming, uninterrupted input to the recorder makes it still more painful to write a CD-R than to do a tape backup. And, the capacity of a single disk is still limited compared to that of a tape cartridge. When digital versatile -- née video -- disc (DVD) becomes more mainstream, and re
cordable DVD (whether DVD-R or any of the rewritable formats) becomes standardized, that medium's greater capacity per disk will make DVD far more competitive with tape.
Library or Jukebox Systems
These aren't generally intended for backup as much as for reasonably quick access to databases (we're no longer talking gigabytes here, but terabytes and, down the road, petabytes). Because they are mechanically complex, with multiple drives and robotic media handling, library systems are not cheap, and they require attention to maintenance and usage. But they sure are faster and cheaper than having armies of people run around and mount tapes upon user request.
Backup Hard Disks
For the simplest of systems, one effective backup choice is to buy an additional hard disk and devote it to storing copies of data or programs. This can be very useful if you don't have to keep a long-term history of what's been done but merely need a backup copy in the event the original hard drive fails. Of co
urse, like any on-site backup system, it won't be a lot of help if the building catches fire.
Removable Media
There's an ever-increasing crop of removable storage products that can also be highly useful and effective as backup. In the 40- to 250-MB category, the most familiar is Iomega's 3-1/2-inch 100-MB Zip disk. SyQuest and Imation have like-capacity products. Additionally, Sony and Fuji Film have just announced a new format called HiFD: a 200-MB floppy disk technology that is backward-compatible with standard floppies. The 1- to 2-GB arena includes products such as Iomega's Jaz Drive, various products from SyQuest, and Castlewood Systems' ORB drive, a new optical disk system that uses 3-1/2-inch removable media with a capacity of 2.16 GB and, the company says, an impressive transfer rate of 12.2 megabytes per second.
| Backup Alternatives
|
|---|
| Magnetic Tape Cartridge
| Library/Jukebox System
| Separate Disk Drive
| Write-Once Optical Media
|
|---|
| Media format
| QIC, Travan, DAT, 8mm
| Tape or optical disk
| | CD-R, WORM, DVD-R
|
| Capacity per media unit
| ****
| ****
| **
| **
|
| Media cost per GB
| *****
| *****
| *
| ****
|
| Equipment cost per GB
| ****
| *
| ****
| ***
|
| Relative time to access stored data
| *
| ***
| *****
| ***
|
| Relative time to back up data
| *
| **
| *****
| ***
|
| Maintenance required for equipment
| **
| *
| *****
| ***
|
| Maintenance required for media
| *
| *
| *****
| *****
|
| Permanence of stored data
| *
| * (tape)
*****(optical)
| ***
| *****
|
| Typical usage scenario
| Daily backup of individual workstations or network segments
| Providing quick, but not instant, access to large volumes (terabytes) of data
| Immediate data availability and system uptime are mission-critical
| Long-term, archival storage; preservation of version histories
|
The Changing Face of Backup
