Back-up
A back-up is a spare copy of data that are on a data carrier. Within every organization it is crucial to make back-ups. Back-up solutions are available in many ways. The most known back-up solution a the tape streamer. This much applied way of back-up is very reliable and is the ideal back-up method for many companies.
Back-up methods (data repository models)
Back-ups at file level are often made like this:
A full back-up per period. The length of the period can depend on the quantity of data, the degree of changes in the data and the capacity of the back-up medium. Often this period is a week, sometimes two weeks or a month. These back-ups are kept longer for archive reasons, even when a newer full back-up has been made.
An incremental back-up per day. In this back-up method only the files are saved that have changed since the previous full or incremental back-up. After a first full back-up made successfully, the incremental back-ups can be deleted. To reassign a complete files folder you will need the most recent full back-up and all incremental back-ups following it.
A progressive back-up, also called incremental forever back-up method. This is a variant of an incremental back-up whereas the first incremental back-up is a full back-up of course. After that only incremental back-ups are made. To reassign a full files folder you do not need different back-ups. Instead the back-up server will build a list of files to be reassigned and sends them from the storage to the client.
Instead of an incremental back-up there’s another possibility, called a differential back-up. In this method all files will be saved that have changed since the previous full back-up. After the next successful full back-up or the next successful differential back-up, all previous differential back-ups can be deleted. To reassign a full files folder you will need the last full back-up and the last differential back-up.
Also simply copying important files is a form of back-up, that can be effective in certain situations.
Storage media
Irrespective of the back-up method, the data need to be saved to a data carrier. There are many different possibilities. Here is a list of them.
Magnetic tape
The magnetic tape is the most common medium for bulk data storage, back-up, archiving and data exchange, since a long time. Tape often has a better capacity / price ratio compared to hard disk, however recently the ratios for tape and hard disk have a smaller difference between one another. There are numerous tape sizes, of which many are brand designated tapes that are compatible with a specific type of server or PC. Tape is a sequential medium, so the access time is slow, the speed of continuous writing or reading of data however is very fast. Some new tape drives are faster than the modern hard drives. A significant advantage of tape is that it has been in use since decades and is known to many people. It is a common medium, and besides much software has been developed and improved since longtime with tape as a back-up medium.
Hard disk
The capacity / price ratio of the hard disk has been improved very much in the recent years, giving the ability for this medium to be competitive to magnetic tape as a bulk storage medium. The most important advantages of storage on hard disk are faster access time, availability, capacity and ease of use. External disk can be connected to the local interfaces as SCSI, USB, FireWire, eSATA, or via long distance technologies like Ethernet, iSCI or Fibre Channel. The most important disadvantages of hard disk back-ups are the risk of damage, especially during transport (for example at off-site back-ups), and that the stability over the years is still unknown.
Optical storage
Systems with Blu-ray disks are more cost efficient than hard disks and magnetic tapes. Some optical storage systems make classified back-ups of data, making the data integrity of optical storage longer. A writable cd can be used as a back-up device. An advantage of cd’s is that they can be reassigned on every machine with a cd-rom drive. (However writable cd-roms are not readable by every system). Besides writable cd’s are relatively cheap. Another common format is recordable dvd. Many optical disk formats are WORM type, which makes them useful for archiving purposes, because the data cannot be altered. Other rewritable formats can be used as well, like cd-rw or dvd-ram.
Software
Infodatek supplies Symantec BackupExec as software for different back-up possibilities. Symantec BackupExec is a good choice for every company. BackupExec has many extra possibilities compared to standard back-up software integrated in the operating system.
You can find more information about Symantec BackupExec here.