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In computing, data loss refers to the unforeseen, usually accidental, loss of data or information and it can happen to YOU. It can happen due to several reasons:
Power failure, resulting in data in volatile memory not being saved to permanent memory.
Hardware failure, such as a head crash in a hard disk.
A software crash or freeze, resulting in data not being saved.
Software bugs or poor usability, such as not confirming a file delete command.
Data corruption, such as file system corruption or database corruption.
A malicious act, such as a worm, virus, hacker or theft of physical media.
A human error, such as accidental file deletion.
or a combination of more than one of the above.
Studies have consistently shown hardware failure and human error to be two most common causes of data loss, accounting for roughly three quarters of all incidents.
There is no guaranteed way to prevent data loss, however, the frequency and impact of data loss can be greatly reduced by taking proper precautions such as: using an uninterrupted power supply, performing regular data backups, regular use of antivirus programs and firewalls, and regular installation of security fixes.
Lost data can often be recovered. There are commercial services that attempt data recovery from physically damaged media. File system corruption can usually be repaired by the user or the system administrator with the right software tools. A deleted file is rarely overwritten on disk; it is more usual for the operating system to simply delete it's entry in the file system index. This can be easily reversed.
Backup in computer terminology refers to "the copying of data for the purpose of having an additional copy of an original source". If the original data is damaged or lost, the data may be copied back from that source, a process which is known as Data recovery or 'Restore'. The "data" may be either data as such, or photos, music, or any other file type that can exist on a computer hard disk. Computer backups are useful primarily for two purposes, the first and most obvious is to restore a computer to an operational state following a disaster. This includes loss of a hard disc or the file system becoming so badly corrupted it cannot be read. The second use often overlooked but probably more common, is to facilitate the recovery of a single file or set of files when they are accidentally deleted or corrupted by the user or a program.
Backup strategies of some type should be implemented by anyone who has information stored on their computer that they do not wish to lose should any type of critical event occur that would cause that data to be erased. Proper backup procedures require redundancy of the backup to a remote location and an effective Backup rotation scheme such as the GFS method (Grandfather-Father-Son Backup). Storing the copy near the original is unwise, since many disasters such as fire, flood and electrical surges are likely to cause damage to the backup at the same time.
A backup should be planned carefully, and the following points should be considered:
Automated backup should be considered, as manual backups can be affected by human error.
Making two copies of a backup can potentially increase security for data recovery, and avoid accidents such as fire and random occurrences. Keeping backup media in safe and secure environments also improves chances of recoverability.
Uncompressed data are easier to recover if the backup media are damaged or corrupted.
Compressing(zipping) data might be important if there is more data than media space on which to store the data.
Backups might take a lot of time to accomplish, which can potentially become a problem in a work environment. Scheduling backups for off-peak times is recommended.
Multiple media backup, for just one content, can be done with independent indexing to optimize individual data recovery.
A regular backup schedule helps ensure that even your most recent data has been saved.
There are primarily three different types of backup - full, incremental, and differential. A full backup is simply the backing up of all the files on the system. An incremental backup will only backup files modified since the last backup. An incremental backup is also referred to as a cumulative incremental backup. A differential backup is a cumulative backup of changes made since the last full backup.
Backup media types
As of 2005, backups are most often made from hard disk to large capacity magnetic tape, hard disk storage, or optical disk media like CD-R and DVD-R. As broadband access becomes more widespread, network and remote backup/online backups are gaining in popularity. There are quite a few companies offering Internet-based backup (Google Keyword Search). During the period 1975–95, most personal/home computer users associated backup mostly with copying floppy disks. The recent drop in hard disk prices and its number one position as the most reliable re-write-able media make it one of the most practical backup media.
A CD or DVD is a excellent alternative backup device. One advantage of CDs/DVDs is that they have a high-density storage media on a 4.75" reflective optical disc. They can hold up to 850 MB/8GB of data respectively. Compare that to a floppy disk that stores only 1.75 mb.
Recovery strategy
A backup is only as useful as its associated recovery strategy. Having a complete set of backup tapes is of no use if the only copy of the software required to read them is on one of the tapes. It is also possible for backup software to run successfully for several months, only to fail when it is needed most due to read errors on the backup media. Magnetic tapes in particular should be read-tested on a regular basis.
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