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Backup tools

Backups are quite an important topic as they provide a second chance in case of a data loss without resorting to the data recovery procedures.

Let's start with some history. Fifteen years ago (as of year 2005), increasing numbers of people had computers, but their important data consisted of small documents and perhaps a few basic programs. To backup all they needed was several blank floppy discs and a compression utility. Even "power users" might find themselves with two megabytes of data to preserve. Modern life is somewhat different and old-fashioned magnetic floppies are just a bit too small for current requirements.

There is a number of media types other than an ancient floppy disk available to place backups at. Many businesses use magneto-optical or large capacity tape drives for their daily and weekly backups. With very high capacities, these devices are technically impressive, but the media are usually very expensive. The common backup media for home and office include CD/DVD discs, dedicated internal and external hard drives. High capacity removable devices similar to Iomega ZIP (100 and 250MB), Jaz (1 or 2GB) and Rev (35GB) are not widespread.

Where cost is a priority, a better option for home and small business users is often disc spanning, where cheap blank media can be used to the same effect as a tape or a dedicated drive. The benefits in cost of disc spanning are easily measurable. For a 20GB backup set the cost per gigabyte (CPG) will be as cheap as 33c for a DVD-RW disc, compared with up to $6 per gigabyte for an external hard drive of comparable size. This makes disc spanning is an attractive and economical option.

This table summarizes storage cost, per gigabyte, for various backup media (based on BestBuy and Iomega data, December 2005). Entries we believe provide the optimum performance for a "home use" backup profile are marked in bold.

Backup size CD-RW DVD-RW Hard disk Iomega Rev
Internal External
700 MB


$1.5 $85 $120 $50
4.5 GB $0.7 $0.33 $19 $26.6 $11
20 GB $0.7 $0.33 $4.25 $6 $2.5
80 GB $0.7 $0.33 $1.06 $1.6 $1.9
250 GB $0.7 $0.33 $0.58 $0.8 $1.6
500 GB $0.7 $0.33 $0.75 $1.08 $1.5

Please note the following additional considerations apply

  • It is not very practical to store backup copy of 250GB on CDRWs for it requires about 360 discs (with a total recording time of about 20 days, assuming 16x recording speed). This explains a shift towards hard disks starting with 80GB (albeit home users rarely need to back up such an amount of changed data on a regular basis).
  • The price of the reader/writer drive is not included into the above calculation. CD/DVD-RW drives are relatively cheap; hard disks do not require any additional accessories; Rev drive is considerably more expensive than a CD/DVD writer device.
  • External hard disks are generally fit backup purpose better than internal ones because they can be easily detached and stored apart of the primary system if required.

Looking at the above table we see that the idea of placing a backup onto several (relatively small) removable disks is still alive and kicking. The following benefits are clear for a typical "home use"

  • It is simple. CD (and DVD) writers are now a part of a basic system configuration, so there is no need to fiddle around with e.g. hard disk reconfiguration.
  • It is reasonably cheap (refer to the table above).
  • Optical discs are removable media, meaning it is easy to store disk sets off-site.
  • Manufacturers estimation of a optical disc shelf-life is about 30 years (compared to an average hard drive lifespan is up to seven years, and up to 20 years for magnetic tapes provided proper maintenance).

We use the same backup approach because our "daily generated difference" (consisting mostly of the source code and HTML documents) is typically well below 100 MB. For this purpose, we utilize Backup Platinum by SoftLogica which is nice, cheap, and simple enough in deployment. In case something large arrives (e.g. a 15GB damaged partition image file) we handle it manually (we use a separate server to backup up less-important, large and rarely updated objects).

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