Full backup, differential backup, and Incremental backup for Databases

Full backup, differential backup, and Incremental backup for Databases

Data backup methods include full backup, differential backup, and Incremental backup. What are the differences between the three backup methods? What should I do in specific applications? This article introduces these issues.

I. Introduction to backup methods

1,Full backup(Full Backup)

Backing up all selected folders does not depend on the file archive attribute to determine which files to back up. During the backup process, any existing tags are cleared, and each file is marked as backed up. In other words, clear the archive attributes.

Full backup refers to a full copy of all data or applications at a certain time point. In practice, a tape is used to completely back up the entire system, including the system and all data. The biggest advantage of this backup method is that you can use only one tape to restore lost data. Therefore, the recovery time of the system or data is greatly accelerated. However, the disadvantage is that there is a large amount of duplicate information in the backup data in each full backup tape. In addition, because each backup requires a large amount of data, the backup takes a long time.

2,Differential backup(Differential Backup)

Back up data that has changed since the last full backup. During differential backup, only selected files and folders marked are backed up. It does not clear the mark, that is, it is not marked as a backup file after backup. In other words, the archive attribute is not cleared.

Differential backupIt refers to the backup that adds or modifies files after a full backup to the differential backup period. During recovery, we only needFirst full backupAndLast differential backup.

For example, on Monday, the network administrator backs up the system completely. On Tuesday, if there is only one more asset list in the system, the Administrator only needs to back up the list together; on Wednesday, an additional product directory was added to the system, so the Administrator not only backed up the directory, but also backed up the list of assets on Tuesday. If you have an additional payroll in the system on Thursday, you need to back up the payroll, product catalog, and asset list on Thursday.

Differential backup not only avoids the defects of the other two backup policies, but also has their own advantages. First, it has the advantage that Incremental backup takes a short time and saves disk space. Second, it has the characteristics that the full backup recovery requires less tape and a short recovery time. The system administrator only needs two tapes, that is, the differential backup tape between the full backup tape and the one day before the disaster occurrence, the system can be restored.

3,Incremental Backup(Incremental Backup)

Data that changes since the last backup (including full backup, differential backup, and Incremental Backup. During the Incremental backup process, only the marked files and folders are backed up. The Marked files are cleared after the backup. In other words, the archive attributes are cleared.
 

Incremental BackupAfter a full backup or the last Incremental backupThe last time compared to the files added and modified. This means that the object for the first Incremental backup is the Files Added and modified after full backup; the object of the second Incremental backup is the added and modified files generated after the first Incremental backup, and so on.

For example, if a system failure occurs on Thursday morning and a large amount of data is lost, the system needs to be restored to Wednesday night. At this time, the administrator needs to first find the full backup tape on Monday for system recovery, then find the tape on Tuesday to restore data on Tuesday, and then find the tape on Wednesday to restore data on Wednesday. Obviously, this is much more difficult than the first strategy. In addition, this type of backup has poor reliability. In this backup, the relationship between tapes is like a chain, which is a ring. Any problem with a tape may lead to a chain disconnection.

The most significant advantage of this backup method is that there is no duplicate backup data, so the backup data volume is not large and the backup time is short. However, Incremental backup data recovery is troublesome. You must have the last full backup and all Incremental backup tapes (once one of the tapes is lost or damaged, the recovery may fail ), they must be restored one by one in the chronological order from full backup to Incremental backup, which greatly prolongs the recovery time.

II,Differences Between Differential backup and Incremental Backup

Through the above conceptual analysis, we can know that the difference between differential backup and Incremental backup is that their backup reference points are different: the former reference point is the last full backup, differential backup or Incremental backup, the reference point of the latter is the last full backup.

The differences between differential backup and Incremental Backup are shown. Cumulative is the differential backup and Differetial Incremental Backup:

 

III,Examples of combined applications of different Backup Types

1. Combination of full backup and differential backup

Taking the weekly data backup plan as an example, we can perform full backup on Monday and differential backup from Tuesday to Friday. If the data is damaged on Friday, you only need to restore the full backup on Monday and the differential backup on Thursday.This type of policy takes much time to back up data, but it takes less time to restore data.

2. Combination of full backup and Incremental Backup

Take weekly data backup as an example. Perform full backup on Monday and Incremental backup from Tuesday to Friday. If data is corrupted on Friday, you need to restore normal backups on Monday and all incremental backups from Tuesday to Friday.This type of policy takes less time to back up data, but it takes more time to restore data.