introduction
A backup server manages spare copies of files. To backup files is to copy files from one store to another. To restore files is to copy them back. A backup server manages the backup and restore process. The second location may be a disk, a CD or a tape. Even the most reliable computer breaks down eventually so one of the cardinal rules in using a computer is back up your files regularly.
BackupPC is an open source server, protected by an open license. A closed backup server is VERITAS NetBackup Server.
what it is
A backup server accepts files and stores them, and accepts requests for stored files and returns them. The word backup is used as a verb and a noun: storing a file is called backing up the file and the file itself is called a backup. The opposite of backup is restore: a client asks for a file and the server returns it. A backup is useful for data security: if a file is removed, accidentally or maliciously, you can restore the file and carry on working. A backup is also useful for disaster recovery: if the entire computer goes bang you can copy everything to a new computer and carry on working.
A simple backup is really no more than a file copy which can be done by any operating system in existence without the use of a server. The server is useful for managing the trickier bits of file backups. It can keep report on which files have been backed up and store several different versions of the same file. The whole backup process can be automated so administrators don't have to worry about backing up files manually.
Backups are sent across the network to a backup server. One server deals with all computers in the network. Sending lots of files across a network creates a packet traffic jam and annoys computer users so backups are either done on a seperate backup network or done on a business data network at a quiet time like 3am.
The store used by a backup server has to be absolutely huge. The size is measured in TB (TeraBytes) which is the technical term for "loads". The two popular types of storage are tapes and disks (no, not CDs or DVDs).
Tapes are the traditional solution from the days when disks had the capacity of a thimble. Each tape holds several GB (GigaBytes) of data, enough for all the files from one computer. A cheap tape backup configuration is a DAT tape drive installed in the computer where the backup server runs. Someone changes the tape when necessary. An expensive setup is a tape silo, a bunch of tape drives, a big rack holding hundreds of tapes and a robotic arm for auto-loading tapes. A tape library of hundreds of tapes covers a big organisation. When you run out of tapes you can buy more.
A tape holds full backups or incremental backups. A full backup is a copy of every file on a computer and an incremental backup is copies of files that have changed since the last backup. Keeping track of these tapes becomes a little complicated. Some tapes are taken to an off-site store to keep them safe if the building burns down, which makes housekeeping a little more complicated. Making daily, weekly and monthly backups and keeping these backup sets for 7 days, 4 weeks and 52 weeks retention respectively is very complicated. Finding a file on a tape can take several minutes of fast forwarding and rewinding.
Disk backups have been around for years but are a lot more recent than tapes. To get terabytes of disk space you have to get a computer with a fat case stuffed with dozens of disks. The good thing is they are much easier to work with. You don't have to bother with incremental backups with disks and you don't have delays reading or writing files. The bad things are:
- a backup computer is expensive to buy and you only have the capacity to back up the computers in a small organisation.
- some disks are screwed into a case or cannot be removed when the computer is on so they are more difficult to carry to an off-site store.
- when you run out of disks you have to buy a whole new computer.
what it isn't
Perfect. If a file is important to you, make your own copy and keep it safe.
where it is
Backup servers are in the administration LAN of the LIC. They use the administration network.
history
Computer users have been watching their hard work go down the toilet for as long as computers have existed.
