When creating a backup strategy, it’s important to understand the different types of backups available and what data each one includes. The main types of backups are full backups, differential backups, and incremental backups. Knowing when to use each can optimize backup time and storage space.
Full Backups
A full backup, also known as a complete backup, contains all the data in the files that are selected for backup. This includes operating systems, applications, settings, and all data files. Full backups represent a complete snapshot of the data at the time the backup was created.
Because full backups contain everything, they take the longest to create and require the most storage space. The advantage is that with a full backup, you can fully restore the entire system. Full backups are recommended for initial backups when first implementing a backup plan, or periodically such as monthly or quarterly.
Differential Backups
A differential backup contains all files that have changed since the last full backup. This allows you to restore data as of the time of the most recent full backup, plus any files that have changed since then. Differential backups offer a middle ground – you don’t have to backup everything each time like a full backup, but you also don’t have to chain multiple incremental backups together during recovery.
Differential backups take less time to create than full backups, but require more storage space because they contain accumulated changes since the last full backup. Using differential backups also allows you to restore data more efficiently compared to incremental backups. Differential backups are commonly created daily or weekly.
Incremental Backups
Incremental backups only contain data that has changed since the most recent backup, whether that’s a full or another incremental backup. This makes them faster to create and smaller in size compared to differential backups. However, to perform a full restore from incremental backups, you need the most recent full backup plus every incremental backup created since then.
Incremental backups are best suited for frequent backups, such as daily or even multiple times per day. The downside is recovering data takes longer because you must restore the full backup first, then apply each incremental backup. Incremental backups minimize storage space but make restores more complex.
Which Backup Types Include Changed Files?
When considering which backup type includes changed files, it helps to think of the progression of backups:
- The full backup contains all files.
- The differential backup contains all changes since the last full backup.
- Incremental backups contain only changes since the most recent backup.
So if you take a new full backup, followed by a differential backup, that differential contains all the files that have changed since the full backup. If you then take an incremental backup, that incremental contains only the files changed since the differential backup.
Full Backup Contents
Full backups, as the name implies, contain the complete contents of the files being backed up. Specifically, a full backup includes:
- All operating system files
- All applications and program files
- All personal files and folders
- Configuration files and settings
- System state information
Everything required to fully restore a system is included in a full backup. No other prior backups are required for recovery.
Differential Backup Contents
Differential backups contain all files that have changed since the most recent full backup. This includes:
- New files created since the full backup
- Files that have been updated since the full backup
- Files that have been deleted since the full backup
Differential backups do not include files that have remained unchanged since the last full backup. This allows them to only contain differences since the full backup.
Incremental Backup Contents
Incremental backups only contain data that has changed since the most recent backup, regardless of backup type. An incremental backup includes:
- Files new or updated since the last incremental or full backup
- Files deleted since the last backup
Incremental backups are the smallest in size because they only contain the changes made since the previous backup.
Comparing Backup Types
Here is a summary comparing the different backup types:
| Backup Type | Contents | Storage Needs | Restore Speed |
|---|---|---|---|
| Full Backup | All files | Highest | Fastest |
| Differential Backup | Files changed since last full backup | Medium | Fast |
| Incremental Backup | Files changed since any backup | Lowest | Slow |
Conclusion
Understanding the differences between full, differential, and incremental backups is key to developing an effective backup strategy. Full backups contain all files, differentials contain changes since the last full, and incrementals contain changes since any backup.
Full and differential backups provide the ability to restore data quickly, while incremental backups conserve storage space. Using a combination of all three backup types allows you to balance restore speed vs storage capacity.
Implementing regular full, differential, and incremental backups ensures you have multiple recovery points to choose from in case you need to restore lost or corrupted data. The goal is to maximize data protection while minimizing backup overhead.