Network Backup - material

Que:- What is Network Backup? Or What is Backup Process?
A network disaster recovery plan is worthless without some way of recovering the data stored on the server.This is where network backup and restore procedures comes in. Making regular backups is a requirement when using computers. Computers can and do fail, and they sometimes fail in ways that make the data stored on them unrecoverable. Also, some turn of events may cause certain important files to be deleted or corrupted. In cases such as these, jobs are saved or lost based on the quality of the backups in place and the ability to restore that important data.
1) Assessing Backup NeedsBefore designing network backup procedures, it is must to understand the company’s backup and restoration needs. Questions such as the following may help in assessing the needs that must meet:

> How dynamic is the data stored on the servers? How often does it change, and in what ways does it
change?
> How much data needs to be backed up, and at what rate is the amount of data growing?
> How much time is available to make the backup?
> If a partial or complete restoration from a backup is required, how quickly must it take place?
As restoring data takes about twice as long as backing it up, although in some cases the times may be
approximately equal.

E.G In other words, if it takes your backup system 10 hours overnight to back up the entire network, it will take 10 to 20 hours to restore that data and this estimate doesn’t include the time required to resolve whatever problem made it necessary to restore data in the first place.
> How many levels of redundancy does the company need in its backups? Most backups are made onto

tapes and support servers that use RAID arrays. In some cases, multiple tapes may be required, each
with a separate copy of the backup.
2) Acquiring Backup Media and Technologies

Once some idea on backup needs are gathered, proceed to acquire the necessary hardware and software to create and manage backups.
If new backup hardware are needed to purchase for a system, then choose from a number good systems, depending on actual needs. When choosing a backup technology, consider the following factors:

Reliability of the hardware and the media
Cost of the hardware and the media
Storage capacity
Likely frequency of restorations
The importance of fitting the entire backup onto a single piece of media

3) Choosing Backup StrategiesAfter acquiring all the necessary information, Now plan a backup rotation strategy, which addresses how
backup media is rotated. Backup rotations are designed to accomplish the following goals:

Rebuild the system with the most recent data possible, in case of a unfortunate failure
Restore files from older tapes that may have been accidentally erased or damaged without anyone noticing the potential loss of data immediately
Protect against backup media failure
Protect the data from an environmental failure, such as a fire, that destroys the original system and data

Most network operating systems maintain special bits for each file on the system. One of these is called the archive bit, which indicates the backup status of the file. When a user modifies a file, its archive bit is set to on, indicating that the file should be backed up. When the backup is accomplished, the archive bit is cleared. Using this archive bit and your backup software, you can make the following types of backups:

A full backup, where all selected directories and files are backed up, regardless of their archive bit state. Full backups clear the archive bit on all of the backed-up files when they are finished.
An incremental backup, where only files with their archive bit set are backed up. This backs up all files changed since the last full or incremental backup. Incremental backups clear the archive bit of the backed-up files; those files will not be backed up during the next incremental backup unless they are modified again and their archive bits are reset to the on state. Incremental backups generally minimize the amount of time needed to perform each daily backup, but they take longer to restore and pose a greater risk of media failure.
A differential backup, which is similar to the incremental backup in that it backs up only files with their archive bits set. The key difference in a differential backup is that the archive bits are left turned on. Subsequent differential backups will back up those same files again, plus any new ones that have been modified. Differential backups take longer to make, but reduce the time required to restore and reduce the risk of media failure.

NOTE:-In a perfect world, it would be nice always to perform full backups. If the system were to fail, then it would need only the most recent backup tape to restore the system fully. However, for a number of reasons, performing a full backup may not always be feasible. For one thing, perhaps there is inadequate time to perform a full backup each day. Another reason is to extend the life of your media and tape drive by
reducing the amount of work that they do. You need to weigh these concerns against the increased time it
takes to restore from a combination of full and incremental or differential backups, and the increased
possibility of being unable to restore backups properly using a combination approach. (For example, if a full restoration required a full backup from the previous week, plus four incremental backups since then, you’re counting on having all five tapes be perfectly good, and you’re somewhat more exposed to a bad tape.)

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