Full Backup
Definition: A full backup involves backing up all selected folders without relying on file archive attributes to determine which files to back up. During this process, any existing marks are cleared, and each file is marked as backed up. In other words, archive attributes are cleared.
Explanation: A full backup refers to making a complete copy of all data or applications at a specific point in time. In practice, this means using a tape to back up the entire system, including the system itself and all data. The major advantage of this method is that it allows for data recovery using just one tape, significantly speeding up the recovery time for systems or data. However, it has drawbacks: each full backup tape contains a large amount of redundant information, and due to the large amount of data that needs to be backed up each time, the backup process itself can be time-consuming.
Differential Backup
Definition: A differential backup involves backing up only the data that has changed since the last full backup. During this process, only the selected files and folders that are marked are backed up. It does not clear these marks, meaning files are not marked as backed up after the backup. In other words, archive attributes are not cleared.
Explanation: Differential backup refers to backing up data that has been added or modified since the last full backup until the time of the differential backup. When performing a recovery, only the first full backup and the last differential backup are needed. Differential backups avoid the drawbacks of the other two backup strategies while retaining their advantages. It offers the benefits of shorter backup times and reduced disk space usage, similar to incremental backups. Additionally, it requires fewer tapes for recovery and shorter recovery times compared to full backups.
Incremental Backup
Definition: An incremental backup involves backing up only the data that has changed since the last backup (including full, differential, or incremental backups). During this process, only the selected files and folders that are marked are backed up. It clears these marks, meaning files are marked as backed up after the backup. In other words, archive attributes are cleared.
Explanation: Incremental backup refers to backing up only the data that has changed since the last full backup or the last incremental backup. This means the first incremental backup includes files added or modified after the full backup, and subsequent incremental backups include changes since the last incremental backup. The significant advantage of this method is that it avoids redundant backup data, resulting in shorter backup times due to smaller data volumes. However, incremental backups complicate data recovery. To restore data, you need the last full backup and all incremental backup tapes in sequence, which can significantly prolong recovery times if any tape is lost or damaged.
Conclusion
Data backups like full, differential, and incremental serve distinct purposes: full backups provide complete snapshots, differentials capture changes since the last full backup, and incrementals save changes since the last backup. Each method balances data completeness with efficiency in storage and recovery processes.