Databases Reference
In-Depth Information
Figure 11-17
Database Server
File Server
Backup Data
Shared network destination.
One of the biggest advantages of this method is its ease of use. Backups can
run fully automated, as long as the network remains available and the destina-
tion server doesn't run out of space. Backups can run very fast, depending on
your network bandwidth. It also leaves the data readily available for recovery
should there be a problem. Some companies, after moving most of their pro-
duction data to PC-based platforms now use some of the extra storage space on
mainframe or minicomputers as a backup destination.
The disadvantage is that the destination computer is a potential point of fail-
ure. Some events, such as fire or flood, could take out both the database server and
the backup file server unless they are kept well separated in different locations.
There is also a potential security concern. You need to ensure that the destination
server is protected against unauthorized access.
The other option used to be more common, backing up to
removable
media,
which is storage media that can be physically removed from the hard
disk. Most often, this means backing up to some kind of magnetic tape, but can
sometimes include optical media such as DVD. One problem with this method
is that the media capacity is often relatively less than the size of the database,
meaning that you need a backup device with a data carousel, or someone has
to physically change the media. This is also why media selections are usually
limited to magnetic tape or DVD. The storage capacity of diskettes and even
writeable CDs is too small for them to be considered for use except in some very
limited situations requiring selected backup of a subset of the database data. A
data carousel
is a backup device that has multiple live media bays, which writes
to several tapes at once, for example, or changes the media for you automati-
cally. Another concern is that magnetic media has a limited lifespan and must
