Glossary Terms
What is differential backup?
When it comes to backup strategies, one common approach is differential backup – but what exactly sets it apart from other types of backup and recovery services? Let’s explore the characteristics and benefits of differential backup and how it compares to other backup methods.
What is differential backup?
Differential backup is a methodology of backup which was created to solve core problems with data backup and recovery services: data changes over time, however all data within a given data set doesn’t all change at once. This could be solved by making a new “full” copy of all data within scope at every backup interval, however that is time and storage intensive.
Differential backup solves these problems by capturing the differences or modifications in data since the last complete backup was performed. This means that each subsequent “differential” backup contains all the changes made since the last full backup, regardless of whether previous differential backups exist.
Differential backup vs. incremental backup: what’s the difference?
A full backup, as the name suggests, creates a complete copy of all selected files and data. It serves as a baseline backup, capturing every bit of information at a specific point in time. On the other hand, differential backup only captures the changes made since the last full backup, making it faster and more efficient in terms of backup time and storage requirements. In many differential backup systems, it is common to perform semi-regular (potentially monthly) full backups and to then perform differential backups on a regular schedule in-between (Eg. hourly, or daily).
Differential and incremental backups are two methods for solving for the storage and data-change over time considerations discussed previously. While differential backup captures changes made since the last full backup, incremental backup takes a different approach. Incremental backup copies the changes made since the last backup, regardless of whether it was a full backup or a previous incremental backup. This means that each subsequent incremental backup captures only the changes made since the previous backup, reducing backup time and storage needs even further.
Benefits of using differential backup
Differential backup offers several advantages that make it a popular choice for many users:
Faster data backup and recovery
Since only the changes made since the last full backup are captured, performing differential backups are generally faster compared to full backups. Additionally, in the event of data loss or system failure, restoring data from a differential backup requires the last full backup and the most recent differential backup, simplifying and expediting the restoration process as compared to an incremental backup model.
Reduced storage requirements
While differential backups require more storage space than incremental backups, they are more space-efficient compared to repeated full backups. By capturing only the changes since the last full backup, differential backups strike a balance between backup size and storage requirements.
Easier management
Differential backup simplifies backup management by maintaining a clear relationship between full backups and subsequent differentials. The backup chain is straightforward, with each differential backup building upon the previous full backup. This makes it easier to track and manage backup sets and versioning.
Considerations when using differential backup
While differential backup offers advantages, it’s essential to consider some factors before implementing this backup strategy:
Increasing backup size over time
Even though they take up less space than full backups, differential backups accumulate all changes since the last full backup and their size grows over time. As a result, storage requirements also increase with each subsequent differential backup. Regularly reviewing data backup and recovery policies and evaluating storage capabilities is crucial to ensure sufficient space for long-term data retention.
Longer restore times
In comparison to incremental backup, differential backup requires a full backup and the most recent differential backup for a complete restore. This can result in longer restore times compared to incremental backups, especially when several differential backups exist.
Conclusion
Differential backup provides a valuable backup strategy that balances backup speed and storage efficiency. By capturing changes made since the last full backup, it offers faster data backup and recovery while requiring less storage space than full backups. However, it’s important to consider factors such as backup size and restore times when deciding on the most suitable backup strategy for your needs.
For more information on the data backup and recovery ecosystem, review CrashPlan’s glossary on data resiliency terminology.
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