Data Backup Equipment
There are many choices you can make about the equipment you use to back up your valuable data. Your decision will depend on factors such as the amount of data that needs to be backed up, the value of the data, how much you can afford to spend on backups and how reliable the backups must be. Here are some common backup equipment types:
|
Backup method
|
Capacity
|
Advantages
|
Disadvantages
|
Suitable for
|
| Floppy disk | 1.4M (1 megabyte= about 1,000,000 bytes: as a guide, the complete text of Shakespeare's Hamlet takes up 177,500 bytes). His complete works in 3 volumes would use 5 floppy disks. |
Everyone has a floppy disk drive | - low capacity - slow - disks wear out and fail easily - magnetic storage can be damaged by magnetism or electric fields |
Home use, small items, unimportant items |
| Ultra-high density floppy disk (e.g. Zip disks, Superdisk LS120) |
>100M | Quite large | - expensive media - still rather slow - still not big enough to back up even a fraction of a home computer's hard disk - still is magnetic storage |
Home use, small business |
| CD-ROM | approx 700M | - most people have CD-ROM drives - optical storage is not affected by magnetism - small storage space needed - cannot be changed after creation (tamper-proof records) - reasonably fast - reasonably cheap |
- CD-ROM disks can be damaged by scratches - can be recorded only once |
Medium-sized businesses - where permanent records need to be made tamper-proof (e.g. you don't want an embezzling employee to be fiddling with old records to cover up theft) |
| CD-RW (re-writeable CD-ROM) |
approx 700M | As above, but: - recordings can be changed - disks can be re-used |
- CD-RW disks cost about 10 times more than plain CD-ROM disks | As above, except tamper-proof histories are not guaranteed |
| DVD-RAM (Writeable DVD) |
5G (about 5,000 megabytes) |
- As for CD - A DVD can back up an entire PC |
As for CD - DVD drives still uncommon in 2001; DVD-RW is rarer still |
As for CD |
| QIC (Quarter-inch cartridges) |
Up to 8-12G | - large capacity - QIC is the standard backup method for file servers |
- magnetic - drives and cartridges relatively expensive* |
Most businesses |
| Internet backup | Unlimited | - slow to upload and download - poor security |
- readily available | - where data may need to accessed from a variety of places |
| A second, duplicate hard disk | 40+ G | - relatively cheap per megabyte - fast -easy to access |
- if your computer is stolen or burnt, your backup dies too | - home business - non-vital data |
* A word about costs: even if a QIC drive cost $1000, the backup software cost $1000 and the cartridges cost $80 each, they indispensible and excellent value for money compared to the costs of recovering lost data.
Keep in mind that the total cost of doing backups is a minuscule fraction of the cost of the data protected by backups. For a business to worry about saving $2000 or so by not properly backing up is false economy. It's also really dumb.
Remember that it's not a question of IF a hard disk will eventually fail: it's a question of WHEN. Hard disks spin at 3600 or 7200 RPM and data is packed in at microscopic scale: they will fail at some stage if left long enough. It's really mind-boggling that they work as reliably as they do!
BACKUP MEDIA
QIC – Quarter Inch Cassette - almost universally used for backing up file servers. They have very high media quality and very large capacity (e.g. 40 to 80 gigabytes)
CD-R, DVD-R - one-time optical recording of data. Once written, it cannot
be changed. This is good when you want to make it impossible for anyone
to "tinker" with the backup later. e.g. if an employee was 'fiddling
the books' to steal money, they could not cover their tracks by changing
old data records burnt to CD or DVD.
Zip disk, SuperDisk - now ancient technology, but still mentioned occasionally.
RAID
- Redundant Array of Independent (or Inexpensive) Disks. Expensive, but very secure and/or fast storage.
Disk mirroring: every time data is written to one hard disk, it is automatically
written to a second identical hard disk.