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.
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.
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
- It is reasonably cheap (refer to the table above).
- Optical discs are removable media, meaning it is easy to store disk sets
- 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).