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1 July 2024  Amanda J. Brook  Senior Product Manager
 

Summary
The article provides an in-depth exploration of differential backups, a data protection method that saves all changes made since the last full backup. It contrasts differential backups with incremental backups, which only save changes since the last incremental backup. The discussion includes the benefits and efficiency of differential backups, particularly in the context of Microsoft SQL Server. The article aims to help readers determine the most suitable backup strategy for their needs by understanding the fundamental differences and applications of these backup methods.



Table of contents

table iconWhat Is a Differential Backup?
table iconFacts About Differential Backup
table iconIncremental vs Differential Backup
table iconDifferential Backup Use Case: Microsoft SQL Server
table iconConclusion
In the realm of data protection, differential backup plays a crucial role alongside its counterpart, the incremental backup. While both methods aim to safeguard data by backing up changes and modifications, they differ significantly in their approach and efficiency. This article delves into the specifics of differential backup, compares it with incremental backup, and highlights its use case in Microsoft SQL Server or some backup softwares. By the end, you’ll have a clear understanding of which backup strategy suits your needs best.

What Is a Differential Backup?

A differential backup is a type of backup that captures all the changes made since the last full backup. Unlike incremental backups that only save changes made since the last incremental backup, each differential backup refers back to the initial full backup. This method ensures that all changes since the last full backup are recorded, making it easier and faster to recover data.
Differential backup: difference from the full backup diagram 

Facts About Differential Backup

  1. Faster to Perform: Performing a differential backup is quicker than executing a full backup.
  2. Storage Growth: Over time, differential backups can become larger than full backups, necessitating periodic full backups.
  3. Ease of Recovery: Recovering files from a differential backup is simpler and faster compared to an incremental backup due to its architecture.

Incremental vs Differential Backup

Both incremental and differential backups are designed to save changes and modifications, but they have distinct differences that impact their storage space, cost, backup speed, and data restoration speed.

Storage Space

A differential backup grows over time as it accumulates all changes since the initial full backup. This makes it slower and more storage-intensive compared to an incremental backup, which only saves changes made since the last incremental backup.

Cost

Differential backups tend to be more costly than incremental backups. The cumulative nature of differential backups means they require more storage space over time, leading to higher resource consumption. This can necessitate additional storage or periodic clean-ups to maintain efficiency.

Backup Speed

Incremental backups are generally faster because they only save changes made since the last backup. In contrast, differential backups save all changes made since the last full backup, making the process slower as more data accumulates.

Data Restoration Speed

The primary goal of any backup strategy is to streamline the restoration process. Differential backups excel by requiring only the initial full backup and the most recent differential backup for recovery, leading to quicker recovery times. In contrast, incremental backups need the initial full backup and all subsequent incremental backups for complete recovery. If any incremental backup is missing or corrupted, the recovery process becomes more complex and time-consuming.

Cloud Compatibility

For those planning digital transformation, the incremental backup technique is often more suitable for cloud environments. It requires less storage space and backup time, reducing the cost of cloud storage. However, the data recovery process can be slower compared to differential backups.
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Differential Backup Use Case: Microsoft SQL Server

To illustrate the practical application of differential backup, let’s examine its use in Microsoft SQL Server. Microsoft SQL Server employs a three-layer backup structure:

Full Backup

Full backup 
A full backup captures the entire database. It is the largest type of backup and is not performed frequently due to its size.

Differential Backup

Differential backup 
An SQL Server differential backup contains all changes since the last full backup. This method allows for backing up only the modified parts of the dataset.

Transaction Log Backup

T-log backup 
A transaction log backup records detailed changes in the database. If both the full and differential backups are lost, the transaction log backup can help recover the latest state of the database. It is typically quicker to perform than full or differential backups. All three backup types complement each other in SQL Server, enabling lower downtime and minimal data loss during restoration.
SQL Server backup chain 

Conclusion

Differential backup is a specialized technique primarily used in environments like SQL Server databases. While it is not suitable for file-level or image-based backups, it offers significant advantages in terms of recovery speed and simplicity. For most other datasets, incremental backup remains the preferred method due to its efficiency in storage and cost. By understanding the differences between these backup strategies, you can make an informed decision that best meets your data protection needs.
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Fullfill different backup needs Supports system backup, disk / partition backup, file backup and disk clone.

Intelligent Automatically analyze the differences between source and backup data.

Convenient Support VSS, allowing to freely view webpages when backing up system.

Highly compatible Supports various files and storage devices.

Quick Backup files at up to 3,000MB/min.

Fullfill different backup needs Backup for disk, partition and system. Save disk space by backing up incremental /differential data.

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Free TrialFree Trial 2000 users have downloaded and enjoy Renee Becca!