Backing up documents is a key disaster-recovery procedure.
For a business that uses information technology in a major way, the data in its computers is of critical value.
While systems can be replaced, business data that's unique to a business cannot be replaced if lost.
Businesses that have lost their data typically close down for good.
- Backing up involves copying data to backup media so that the data can be restored in case the original data is lost. The emphasis is on data disaster recovery—distinct from document archiving where the emphasis is on preserving primary data for historical and other purposes. The different objectives lead to different practices.
- Data can be lost in many ways, such as natural disasters like fire or flood, man made disasters like accidental wholesale deletion of data, or malicious actions such as theft or virus attacks. They can also be lost due to technical problems such as power surges or system crashes.
- Backing up data is not a simple task of copying original data to secondary media. Where the volume of data is large, the backup storage media required can number in the hundreds. Unless redundant data is cleared, large sums of money can be wasted on an unnecessarily huge volume of backup media.
- In addition to the volume of backup media, there's also the issue of organizing them in a manner that ensures quick retrieval of relevant media when a restore operation becomes necessary. Unless details exist, such as what data has been backed up to which disk and when, recovering from a data loss disaster can become a chaotic affair, if not impossible.
- Details of backed up data, such as media volume IDs and what each contains, can be stored as paper lists where the volume is small and in computer databases where the volume is large. Maintaining such details can also help reduce the number of media requirements because redundant backups can be minimized.
- Proper policies should be in place regarding backup procedures. Taking full backups of all data in the computer systems daily is a wasteful exercise, and it can lead to copying a large volume of duplicate data. Another policy issue is determining the data that needs to be backed up. This can include non-file data such as system descriptions, partition layout details, system-configuration details, and file metadata.
- Data can be backed up using different schemes, such as 'full plus incremental', 'Towers of Hanoi', and 'incremented media'. The objective of all schemes is to ensure that all critical data is backed up and that duplication is minimized. For example, one full backup is taken at specific intervals, and only new and changed data are backed up from one full backup to the next full backup. The second and subsequent series of backups reuse the earlier media to reduce media requirements.
- Backup storage media can come in the form of magnetic tape (which has been in use for a long time, and whose characteristics are well known), hard disks in local or remote drives, optical disks such as CD or DVD that are easy to carry around and store, solid state media such as USB flash drives or SSDs, and third-party storage space on the World Wide Web. Some media can degrade and lose stored data as in the case of optical media. Data that need to be stored for longer periods should not be kept on such media.
- Backup media can be online to facilitate quick restoration in case of data loss, near-line as in a robot-controlled device that retrieves the relevant media and mounts it on an online drive in milliseconds, or offline when the media has to be located and mounted manually. While the online and near-line media enable quick restoration, they are vulnerable to online risks such as virus attacks or technical problems that affect the system.
- Copying open files presents certain problems, such as the file content changing between the start and finish of the backup process. In larger organizations, specific backup windows (time periods) are allocated for the backup process. These would be periods when there will be a minimum of system usage.
- Several methods are used to reduce storage space requirements of backed-up data. These include data compression and de-duplication. Encryption is used to maintain confidentiality of the data.
- Considering the numerous issues involved in backing up data, it's often considered better to entrust the job to specialist service providers. In this case you're entrusting confidential data to a third party, and the service providers should be reputed and trustworthy organizations. Encryption of data is another safeguard in such cases.
Backing up the data that organizations accumulate can prove mission-critical when the original data become lost or destroyed. Storing the backup in offsite locations can also prove critical. Cases have been reported when IT staff had to run into burning buildings to save backup tapes (and yet still lose much of the data). Therefore, offline and offsite storage of periodically backed up data is the preferred alternative.
