3.6 Disaster recovery
Backup Types: Each backup type differs primarily in the amount backed up and whether the items being backed up have changed.
There are three backup types:
Full backup:Full backups typically back up the entire contents of a server, whether they've changed or not.
Incremental backup:An incremental backup stores all files that have changed since the last Full, Differential, or Incremental backup. The chief advantage of an incremental backup is that it takes the least time to complete, and requires less storage space. However, during a restore operation, you need to process each incremental back for complete restoration. This could result in a lengthy restoration time compared to Full and/or Differential backups.
Differential backup:A differential backup contains all files that have changed since the last full backup. The advantage of a differential backup is that it shortens the backup and restore time compared to a full backup and incremental backup.
Tape Rotation Schedule: The rotating backup tapes is the easiest way to manage a tape backup scheme. Some of the rotations are,
Weekly Rotation: Weekly Rotations are the simplest one. A tape is assigned to each weekday and labeled with the name of the day. There will be five tapes and each tapes are overwritten as the day of the week comes again.
Monthly Rotation:Monthly rotation will help in restoring data for an entire month. Managing this type of backup scheme is more complicated because more tapes must be kept in track.
Yearly Rotation: Yearly backup can be build on top of the monthly system. The tapes needed are 12, one for each month, labeled with the names of the months.
Grandfather-Father-Son Rotation: Grandfather-Father-Son method is one of the most commonly used tape backup schemes. With this rotation backups are taken daily, weekly, and montly. The daily incremental backups are known as the Son, because the daily taps are reused after a week. The last full backup of the week is known as the Father, because the weekly tapes stay for a month and are reused during next month. The last full backup of the month is known as the Grandfather. Grandfather tapes are the oldest and are retained for a year before reusing them. Note that the G-F-S is a hierarchical backup mechanism, and it can be used for backing up using CD media as well, in the same way it is used for tape backup.
Virus Protection: A virus is a program that causes malicious change in your computer and makes copies of it. Sophisticated viruses encrypt and hide themselves to thwart detection.
File viruses : A file virus attacks executable application and system program files, such as those ending in .COM, .EXE and .DLL. Most of these types of viruses replace some or all of the program code with their own.
Macro viruses : A macro is a command script that is used to automatically perform operations without a user's intervention. A Macro virus, for example, may use the Visual Basic macro-scripting language to perform malicious or mischievous functions in data files created with MS Office products.
Boot Sector viruses : Boot sector viruses affect the master boot record (MBR) of a computer. MBR is track one, sector one on your hard disk. Any computer, at bootup, checks MBR to find a pointer for the operating system. A boot sector virus will overwrite the boot sector, thereby making it look as if there is no pointer to your operating system.
Scanning for viruses: An anti-virus scan is the process in which an anti-virus program examines the computer suspected of having a virus and eradicates any virus it finds. There are two types of anti-virus scans:
An on-demand scan searches a file, a directory, a drive, or an entire computer. An on-access scan checks only file you are currently accessing. To maximize the protection both should be used in combination.
One most frequently used application for on-access scan is email access. When you are using, say Thurnderbird (a Mozilla email client program) to access email, an on-demand anti-virus program kicks-in, and scans incoming email One such program, free for home use, is AVG Antivirus program. AVG is both an on-demand, and on-access anti-virus package.
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