Encyclopedia of Computer Science and Technology

ackup and archive systems 37Ease of Use: To the extent backups must be set up or initiatedby human operators, is the system easy to understandand use with minimal training? Ease of use bothpromotes reliability (because users will be more likelyto perform the backups), and saves money in trainingcosts.Economy: How does a given system compare to others interms of the cost of the devices, software, media (suchas tapes or cartridges), training, and administration?The market for storage and backup software and serviceshas grown rapidly in the mid-2000s, driven in part bya new awareness of the need of corporations to protect theirvital data assets from natural disasters or possible terroristattacks (see cyberterrorism and disaster planning andrecovery). In many corporations the amount of data thatneeds to be backed up or archived grows at a rate of 50 percentper year or more.Choice of MethodsThe actual choice of hardware, software, and media dependsconsiderably on how much data must be backed up (andhow often) as well as whether the data is being generatedon individual PCs or being stored at a central location. (Seefile server, data warehouse.)Backups for individual PCs can be accomplished usingthe backup software that comes with various versions ofMicrosoft Windows or through third-party software.In addition to traditional tapes, the media used includeCDs or DVDs (for very small backups), tiny USB “flashdrives” (generally up to a few gigabytes of data), cartridgedrives (up to 70 gigabytes or more), or even compact externalUSB hard drives that can store hundreds of gigabytes.(see cd and dvd rom, flash drive, hard drive, tapedrive, and usb.)In addition to backing up documents or other data generatedby users, the operating system and applications softwareis often backed up to preserve configuration informationthat would otherwise be lost if the program were reinstalled.There are utilities for Microsoft Windows and other operatingsystems that simplify the backing up of configurationinformation by identifying and backing up only those files(such as the Windows Registry) that contain informationparticular to the installation.The widespread use of local area networks makes it easierto back up data automatically from individual PCs andto store data at a central location (see local area networkand file server). However, having all data eggs inone basket increases the importance of building reliabilityand redundancy into the storage system, including the useof RAID (multiple disk arrays), “mirrored” disk drives, anduninterruptible power supplies (UPS). Despite such measures,the potential risk in centralized storage has led toadvocacy of a “replication” system, preferably at the operatingsystem level, that would automatically create backupcopies of any given object at multiple locations on the network.Another alternative of growing interest is the use of theInternet to provide remote (off-site) backup services.By 2005 Gartner Research was reporting that about94 percent of corporate IT managers surveyed were usingor considering the use of “managed backup” services.IDC has estimated that the worldwide market for onlinebackup services would reach $715 million by 2011. Onlinebackup offers ease of use (the backups can be run automatically,and the service is particularly handy for laptopcomputer users on the road) and the security of off-sitestorage, but raise questions of privacy and security of sensitiveinformation, particularly if encryption is not builtinto the process. Online data storage is also provided toindividual users by a variety of service providers such asGoogle. Application Service Providers (ASPs) have a naturalentry into the online storage market since they alreadyhost the applications their users use to create data (seeapplication service provider).A practice that still persists in some mainframe installationsis the tape library, which maintains an archive of dataon tape that can be retrieved and mounted as needed.ArchivingAlthough using much of the same technology as makingbackups, archiving of data is different in its objectives andneeds. An archive is a store of data that is no longer neededfor routine current use, but must be retrievable upondemand, such as the production of bank records or e-mailas part of a legal process. (Data may also be archived forhistorical or other research purposes.) Since archives mayhave to be maintained for many years (even indefinitely),the ability of the medium (such as tape) to maintain datain readable condition becomes an important consideration.Besides physical deterioration, the obsolescence of file formatscan also render archived data unusable.Management ConsiderationsIf backups must be initiated by individual users, the usersmust be trained in the use of the backup system and motivatedto make backups, a task that is easy to put off toanother time. Even if the backup is fully automated, samplebackup disks or tapes should be checked periodically tomake sure that data could be restored from them. Backuppractices should be coordinated with disaster recovery andsecurity policies.Further ReadingBackup Review. Available online. URL: http://www.backupreview.info/index.php. Accessed April 22, 2007.Jacobi, Jon L. “Online Backup Services Come of Age.” PC WorldOnline, July 28, 2005. Available online. URL: http://www.pcworld.com/article/id,121970-page,1-c,utilities/article.html.Accessed April 22, 2007.Jackson, William. “Modern Relics: NIST and Others Work on Howto Preserve Data for Later Use.” Available online. URL: http://www.gcn.com/print/25_16/41069-1.html. Accessed April 22,2007.Storage Search. Available online. URL: http://www.storagesearch.com/. Accessed April 22, 2007.Preston, W. Curtis. Backup & Recovery. Sebastapol, Calif.: O’ReillyMedia, 2006.