The need to create backup copies of data has become increas-ingly important as dependence on computers has grown and
the economic value of data has increased. Potential threats to data include bugs in the operating system or software applications, malicious acts such as the introduction of computer viruses, theft, hardware failure (such as in hard disk drives), power outages, fire, and natural disasters such as earthquakes and floods.
A variety of general principles must be considered in devising an overall strategy for creating and maintaining backups:
Reliability: Is there assurance that the data is stored accu-rately on the backup medium, and will automatic back-ups run reliably as scheduled? Can the data be accurately retrieved and restored if necessary?
Physical storage: Is the backed-up data stored securely and organized in a way to make it easy to retrieve particular disks or tapes? Is the data stored at the site where it is to be used, or off-site (guarding against fire or other disas-ter striking the workplace).
Ease of Use: To the extent backups must be set up or initi-ated by human operators, is the system easy to under-stand and use with minimal training? Ease of use both promotes reliability (because users will be more likely to perform the backups), and saves money in training costs.
Economy: How does a given system compare to others in terms of the cost of the devices, software, media (such as tapes or cartridges), training, and administration?
The market for storage and backup software and ser-vices has grown rapidly in the mid-2000s, driven in part by a new awareness of the need of corporations to protect their vital data assets from natural disasters or possible terrorist attacks (see cyberterrorism and disaster planning and recovery). In many corporations the amount of data that needs to be backed up or archived grows at a rate of 50 per-cent per year or more.
the economic value of data has increased. Potential threats to data include bugs in the operating system or software applications, malicious acts such as the introduction of computer viruses, theft, hardware failure (such as in hard disk drives), power outages, fire, and natural disasters such as earthquakes and floods.
A variety of general principles must be considered in devising an overall strategy for creating and maintaining backups:
Reliability: Is there assurance that the data is stored accu-rately on the backup medium, and will automatic back-ups run reliably as scheduled? Can the data be accurately retrieved and restored if necessary?
Physical storage: Is the backed-up data stored securely and organized in a way to make it easy to retrieve particular disks or tapes? Is the data stored at the site where it is to be used, or off-site (guarding against fire or other disas-ter striking the workplace).
Ease of Use: To the extent backups must be set up or initi-ated by human operators, is the system easy to under-stand and use with minimal training? Ease of use both promotes reliability (because users will be more likely to perform the backups), and saves money in training costs.
Economy: How does a given system compare to others in terms of the cost of the devices, software, media (such as tapes or cartridges), training, and administration?
The market for storage and backup software and ser-vices has grown rapidly in the mid-2000s, driven in part by a new awareness of the need of corporations to protect their vital data assets from natural disasters or possible terrorist attacks (see cyberterrorism and disaster planning and recovery). In many corporations the amount of data that needs to be backed up or archived grows at a rate of 50 per-cent per year or more.
Choice of Methods
The actual choice of hardware, software, and media depends considerably on how much data must be backed up (and how often) as well as whether the data is being generated on individual PCs or being stored at a central location. (See file server, data warehouse.)
Backups for individual PCs can be accomplished using the backup software that comes with various versions of Microsoft Windows or through third-party software.
In addition to traditional tapes, the media used include CDs or DVDs (for very small backups), tiny USB “flash drives” (generally up to a few gigabytes of data), cartridge drives (up to 70 gigabytes or more), or even compact exter-nal USB hard drives that can store hundreds of gigabytes. (see cd and dvd rom, flash drive, hard drive, tape drive, and usb.)
In addition to backing up documents or other data gener-ated by users, the operating system and applications software is often backed up to preserve configuration information that would otherwise be lost if the program were reinstalled. There are utilities for Microsoft Windows and other operat-ing systems that simplify the backing up of configuration information by identifying and backing up only those files (such as the Windows Registry) that contain information particular to the installation.
The widespread use of local area networks makes it eas-ier to back up data automatically from individual PCs and to store data at a central location (see local area net-work and file server). However, having all data eggs in one basket increases the importance of building reliability and redundancy into the storage system, including the use of RAID (multiple disk arrays), “mirrored” disk drives, and uninterruptible power supplies (UPS). Despite such mea-sures, the potential risk in centralized storage has led to advocacy of a “replication” system, preferably at the operat-ing system level, that would automatically create backup copies of any given object at multiple locations on the net-work.
Another alternative of growing interest is the use of the Internet to provide remote (off-site) backup services.
By 2005 Gartner Research was reporting that about 94 percent of corporate IT managers surveyed were using or considering the use of “managed backup” services. IDC has estimated that the worldwide market for online backup services would reach $715 million by 2011. Online backup offers ease of use (the backups can be run auto-matically, and the service is particularly handy for laptop computer users on the road) and the security of off-site storage, but raise questions of privacy and security of sen-sitive information, particularly if encryption is not built into the process. Online data storage is also provided to individual users by a variety of service providers such as Google. Application Service Providers (ASPs) have a natu-ral entry into the online storage market since they already host the applications their users use to create data (see application service provider).
A practice that still persists in some mainframe installa-tions is the tape library, which maintains an archive of data on tape that can be retrieved and mounted as needed.
Archiving
Although using much of the same technology as making backups, archiving of data is different in its objectives and needs. An archive is a store of data that is no longer needed for routine current use, but must be retrievable upon demand, such as the production of bank records or e-mail as part of a legal process. (Data may also be archived for historical or other research purposes.) Since archives may have to be maintained for many years (even indefinitely), the ability of the medium (such as tape) to maintain data in readable condition becomes an important consideration. Besides physical deterioration, the obsolescence of file for-mats can also render archived data unusable.
Management Considerations
If backups must be initiated by individual users, the users must be trained in the use of the backup system and moti-vated to make backups, a task that is easy to put off to another time. Even if the backup is fully automated, sample backup disks or tapes should be checked periodically to make sure that data could be restored from them. Backup practices should be coordinated with disaster recovery and security policies.
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