Speed vs. accuracy in backup and restore.The purpose of backing up business-critical data is to enable an accurate restore when data loss occurs. Backups have to run as quickly as possible in order to protect the multiple gigabytes of data that reside on typical networks of servers, desktops and notebooks. Ideally, backup software See backup program. (tool, software) backup software - Software for doing a backup, often included as part of the operating system. Backup software should provide ways to specify what files get backed up and to where. would offer both fast backups and 100% accurate restores. Unfortunately, backup administrators have had to compromise between speed and accuracy because traditional backup software forces a choice between slow backups with accurate restores or fast backups with inaccurate restores. Full Backups See backup types. : Accuracy Without Speed With traditional backup software, time-consuming time-con·sum·ing adj. Taking up much time. time-consuming Adjective taking up a great deal of time Adj. 1. full backups are the only way to ensure completely accurate restores. A full backup copies data from all of the computers selected for backup onto the backup media. Restores place all of the data from the backup media onto the selected computers. However, full backups take too long to run because large amounts of information have to be transferred. Often, computers that are low on the backup list are not backed up if there is not enough time to copy their data. To correct this problem, backup administrators must carefully review backup logs each day and write new scripts to backup the specific files, folders and computers that were missed during the previous backup window. Some computers might still remain unprotected despite these additional steps. As a result, organizations often settle for protecting only a fraction of their computers rather than dealing with the complexity and manual effort involved in trying to back up too much data in too little time. Incremental Additional or increased growth, bulk, quantity, number, or value; enlarged. Incremental cost is additional or increased cost of an item or service apart from its actual cost. and Differential Backups See backup types. (operating system) differential backup - A kind of backup that copies all files that have changed since the last full backup. Each differential backup will include all files in previous differential backups since the full backup so to restore a version of : Speed Without Accuracy Typically, incremental or differential backups are used as a concession CONCESSION. A grant. This word is frequently used in this sense when applied to grants made by the French and Spanish governments in Louisiana. to the time constraints In law, time constraints are placed on certain actions and filings in the interest of speedy justice, and additionally to prevent the evasion of the ends of justice by waiting until a matter is moot. that exist in most businesses. Fast backups are achieved by running an initial full backup followed by periodic incremental or differential backups. Incremental backups See backup types. (operating system) incremental backup - A kind of backup that copies all files which have changed since the date of the previous backup. The first backup of a file system should include all files - a "full backup". Call this level 0. contain only files that have changed since the previous full or incremental backup. This creates a series of incremental backup media sets, each containing the information that changed since the previous backup. Differential backups contain only files that have changed since the initial full backup. Because the amount of changed data increases over time, differential backups consume increasingly more time and media, until it becomes more efficient to run another full backup and begin the differential backup cycle again. Because incremental and differential backups copy only files that are new or have changed, they are faster than full backups and consume less media space. They can run on a regular schedule within a reasonable amount of time, allowing a company to safeguard the most recent information on all computers. Although incremental and differential backups are faster than full backups, restoring from them is more complex and the restore is always flawed flaw 1 n. 1. An imperfection, often concealed, that impairs soundness: a flaw in the crystal that caused it to shatter. See Synonyms at blemish. 2. when restoring more than a single file. During a restore, the files and folders from the full backup are returned to the hard drive, followed by data from the series of incremental backups or from the latest differential backup. This method of performing restores is flawed because the process restores all the contents of the full backup plus all the contents of the required incremental or differential backups, including previously deleted Deleted A security that is no longer included on a specified market. Sometimes referred to as "delisted". Notes: Reasons for delisting include violating regulations, failing to meet financial specifications set out by the stock exchange and going bankrupt. , moved, or renamed files and folders. How Flawed Restores Occur To understand how flawed restores occur, consider the following example of a backup cycle that begins with a lull backup and continues with daily incremental or differential backups. After the restore, the user discovers that File B is back, even though it was deleted. File A and File C are back, even though they were renamed. And File D appears both in its original location and in its new location. The stone kinds of problems can occur for restored folders as well. Without an accurate restore, the time saved by running incremental or differential backups is clearly not a benefit because it is difficult, or even impossible, to clean up the hard drives after the flawed restore. Progressive Backup: Speed and Accuracy Another type of backup strategy, Progressive Backup, allows for speedy incremental backups, but uses a different technique to provide accurate restores that do not place unwanted deleted, moved, or renamed files and folders back onto a drive. Before a daily backup is performed, Progressive Backups take a list of all of the files and folders on the hard drives being backed up. When a restore takes place, that list is used as a guide so that only the correct files and folders are restored onto the hard drives. The result is an accurate restore. No unwanted files or folders that were previously deleted, renamed, or moved are mistakenly mis·tak·en v. Past participle of mistake. adj. 1. Wrong or incorrect in opinion, understanding, or perception. 2. Based on error; wrong: a mistaken view of the situation. placed onto the hard drives. Progressive Backup provides the speed and flexibility of daily incremental or differential backups while providing the restore accuracy of full backups. It also enables fast backups that can run more frequently and protect all business-critical data on the selected computers during limited backup windows. It allows businesses to protect more computers, keeping information complete and up-to-date without requiring complicated backup schedules. A progressive backup can automatically recognize identical files on all of the computers on the network. It then transfers only one copy of each unique file to the backup media, saving considerable space and time. For example, if 20 desktop PCs running Windows XP The previous client version of Windows. XP was a major upgrade to the client version of Windows 2000 with numerous changes to the user interface. XP improved support for gaming, digital photography, instant messaging, wireless networking and sharing connections to the Internet. are being completely backed up, only one copy of identical operating system operating system (OS) Software that controls the operation of a computer, directs the input and output of data, keeps track of files, and controls the processing of computer programs. files will be moved to the backup media. If identical copies of a 20 MB PowerPoint A presentation graphics program from Microsoft for Macintosh and Windows. It was the first desktop presentation program for the Mac and provides the ability to create output for overheads, handouts, speaker notes and film recorders. presentation exist on 10 different computers, only one copy of the presentation will be backed up. Speed and Accuracy A fundamental problem with backup and restore involves compromising between fast backups and accurate restores. Full backups provide accurate restores, but take too long to run. Incremental or differential backups save time, but result in flawed restores that mistakenly retrieve To call up data that has been stored in a computer system. When a user queries a database, the data are retrieved into the computer first and then transmitted to the screen. (language) Retrieve files and folders that have been previously deleted, renamed, or moved. As a result, traditional backup software forces you to choose between speed and accuracy. With Progressive Backups, there is no compromise between speed and accuracy. Combining speed and accuracy provides a range of benefits, including complete protection for data, confidence in the quality of the restores, and minimal administrative headaches for an IT department. Progressive Backup delivers the best qualities of incremental, differential, and full backups--without sharing their significant problems. Various versions of software that use Progressive Backup technology are tailored for small and medium businesses, departments within larger corporations, or for home and small offices.
Day 1 Day 2 Day 3 Day 4 Day 5
File A File A renamed File F File F File F
to File F deleted
File B File B deleted
File C File C renamed File G File G File G
to File G
File D File D moved File D File D
to new location new location deleted
File E File F File E File E File E
Figure 1- File changes during a typical backup schedule
Files from Files from Day 3 Hard Drive after a
Day 1 FULL INCREMENTAL/ restore to Day 3
Backup DIFFERENTIAL backup
File A File F File A-Wrong
File F
File B File B-Wrong
+ =
File C File G - File C-Wrong
File G
File D File D (new location) File D-Wrong
File D (new location)
File E
Figure 2- Flawed restore to Day 3 for the computer files shown in
Figure 1
Day 1 Day 2 Day 3 Day 4 Day 5
File A File A renamed File F File F File F
to File F deleted
File B File B deleted
File C File C renamed File G File G File G
to File G
File D File D moved File D File D
to new location (new location) deleted
File E File E File E File E File E
Figure 3- File changes during a typical backup schedule
Required files Required files from Day 2 Hard Drive after a
from Day 1 & Day 3 INCREMENTAL restore to Day 3
FULL backups
Backup
File F File F
+ =
File G File G
File D (new location) File D (new location)
File E File E
Figure 4- A 100% accurate restore to Day 3 for the computer files
in Figure 3
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