useful for a home or small business. CD writers and media that were once
very common are cheap if you can find them but are gradually disappearing,
and automated CD-changing machines, necessary for automatically backing
up large amounts of data, are still quite costly, if you can find them at all. A
benefit of CD and DVD storage over tape devices is that the archived
uncompressed file system can be mounted and its files accessed randomly,
just as with a hard drive, making the recovery of individual files easier. (This
is similar to creating a data CD; see Chapter 6, “Multimedia Applications.”)
Each CD-RW disc can hold 650MB to 700MB of data, and larger chunks of
data can be split to fit on multiple disks. Some backup programs support this
method of storage. After these discs are burned and verified, the shelf life for
the media is at least a decade or longer.
DVD+RW/-RW is similar to CD-RW, but it is more expensive and can store
up to 8GB of uncompressed data per disc.
Honestly, though, discs are an old technology, and although they haven’t
completely died off, the use of either CDs or DVDs for backup has dropped
off considerably. It won’t be long before they become almost as rare as floppy
disks and drives.
Network Storage
For network backup storage, remote arrays of hard drives provide one
solution to data storage. With the declining cost of mass storage devices and
the increasing need for larger storage space, network storage (NAS, or
network-attached storage) is available and supported in Linux. Network
storage involves cabinets full of hard drives and their associated controlling
circuitry, as well as special software to manage all of it. NAS systems are
connected to the network and act as huge (and expensive) mass storage
devices.
More modest and simple network storage can be done on a remote desktop-
style machine that has adequate storage space (up to eight 1TB drives is a lot
of storage space, easily accomplished with off-the-shelf parts), but then that
machine and the local system administrator have to deal with all the problems
of backing up, preserving, and restoring the data. Several hardware vendors
offer such products in varying sizes.
Tape Drive Backups
Tape drives have been used in the computer industry from the beginning.