Incremental Backup

A.

One of the key item to understand regarding backup is the archive bit.

The archive bit is used to determine what files have been backuped already.

The archive bit is set if a file is modified or a new file is created, this indicates to the backup program that it has to be saved on the next backup.

When a full backup is performed the archive bit will be cleared indicating that the files were backup.

This allows backup programs to do an incremental or differential backup that only backs up the changes to the filesystem since the last time the bit was cleared Full Backup (or Reference Backup) A Full backup will backup all the files and folders on the drive every time you run the full backup.

The archive bit is cleared on all files indicating they were all backuped.

Advantages: All files from the selected drives and folders are backed up to one backup set.

In the event you need to restore files, they are easily restored from the single backup set.

Disadvantages: A full backup is more time consuming than other backup options.

Full backups require more disk, tape, or network drive space.

Incremental Backup - An incremental backup provides a backup of files that have changed or are new since the last incremental backup.

For the first incremental backup, all files in the file set are backed up (just as in a full backup)

If you use the same file set to perform a incremental backup later, only the files that have changed are backed up.

If you use the same file set for a third backup, only the files that have changed since the second backup are backed up, and so on.

Incremental backup will clear the archive bit.

Advantages: Backup time is faster than full backups.

Incremental backups require less disk, tape, or network drive space.

You can keep several versions of the same files on different backup sets.

Disadvantages: In order to restore all the files, you must have all of the incremental backups available.

It may take longer to restore a specific file since you must search more than one backup set to find the latest version of a file.

Differential Backup - A differential backup provides a backup of files that have changed since a full backup was performed.

A differential backup typically saves only the files that are different or new since the last full backup.

Together, a full backup and a differential backup include all the files on your computer, changed and unchanged.

Differential backup do not clear the archive bits.

Advantages: Differential backups require even less disk, tape, or network drive space than incremental backups.

Backup time is faster than full or incremental backups.

Disadvantages: Restoring all your files may take considerably longer since you may have to restore both the last differential and full backup.

Restoring an individual file may take longer since you have to locate the file on either the differential or full backup.

For more info see: http://support.microsoft.com/kb/136621 Source: KRUTZ, Ronald L.

& VINES, Russel.

D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 69.

The correct answer is C. Incremental backup method.

The incremental backup method copies only the files that have changed since the last backup, whether it was a full backup or an incremental backup. It does not clear the archive bit, which is a file attribute that indicates whether a file has been modified since the last backup.

This means that if you perform an incremental backup, you will only back up the changes made since the last backup, which can save time and storage space compared to a full backup. However, you will need to keep track of which files have been backed up, as well as the order in which the backups were made, in order to be able to restore the data correctly.

In contrast, the differential backup method copies all the files that have changed since the last full backup, but it does not take into account any previous incremental backups. This means that each differential backup can be larger than the previous one, which can lead to longer backup times and larger backup files.

The full backup method copies all the data on a system or device, regardless of whether it has changed since the last backup. This method is useful for creating a complete backup of a system or device, but it can be time-consuming and use a lot of storage space.

Finally, the tape backup method refers to using magnetic tape as a backup medium. It can be used with any of the backup methods described above, but it is becoming less common as other backup media, such as hard drives and cloud storage, have become more affordable and reliable.