Differential Backup Guide 

This article provides an overview of differential backup and its unique characteristics. Join us to gain a comprehensive understanding of this backup method and its differences from other backup strategies you can use in your network environment.

What is differential backup? 

Differential backup is a type of data backup method that is commonly used in computer systems to protect and preserve data. It is designed to back up only the data that has changed or been modified since the last full backup.

In a differential backup, the first backup is typically a full backup that copies all the selected files and folders to a backup destination. After the initial full backup, subsequent differential backups only include the files and folders that have changed or been added since the last full backup. This means that each differential backup contains all the changes made since the last full backup, regardless of whether previous differential backups were performed.

The advantage of using differential backups is that they can be faster and require less storage space compared to performing full backups every time. When it comes to restoring data, you only need the last full backup and the latest differential backup to restore all the data up to the point of the most recent differential backup. This can simplify the restoration process and reduce the time required to recover data.

However, one drawback of differential backups is that as time passes and more differential backups are performed, the size of the backups increases. This can result in longer backup times and larger storage requirements. Additionally, if any differential backup in the chain is corrupted or lost, subsequent differential backups relying on it may be rendered useless.

It’s worth noting that there are other backup methods available, such as incremental backups, which only back up the changes made since the last backup, regardless of whether it was a full or differential backup. The choice of backup method depends on factors such as data size, available storage, and the desired recovery time.

How does differential backup work?

Differential backups work by capturing and storing only the data that has changed or been modified since the last full backup. Here’s a step-by-step explanation of how the process typically works:

1. The first step is to perform a full backup, which involves copying all selected files and folders from the source system to a backup destination. This initial backup serves as a baseline and captures the entire dataset
2. After the full backup, subsequent differential backups come into play. A differential backup captures all the changes made since the last full backup. This includes new files and folders as well as any modifications to existing files.
3. To determine which files and folders have changed, the backup software compares the attributes, timestamps, or content of the files against the information recorded during the full backup. Any files that differ from their corresponding versions in the full backup are marked as changed.
4. Once the changes are identified, the differential backup process copies only the changed files and folders to the backup destination. It does not repeat the process of copying the unchanged data that was already captured in the full backup.
5. Each subsequent differential backup continues to capture all the changes made since the last full backup, regardless of previous differential backups. This means that each differential backup accumulates all the changes made up to that point.
6. To restore data from a differential backup, you need the most recent full backup and the latest differential backup. By applying the differential backup to the full backup, you can restore all the data up to the point of the most recent differential backup.

It’s important to note that while differential backups simplify the restoration process by requiring only the most recent full backup and the latest differential backup, the size of the backups can increase over time. As more differential backups are performed, the amount of changed data accumulates, potentially leading to larger backup sizes and longer backup durations.

Why use differential backup?

Differential backups offer several advantages and are used for various reasons in data backup strategies. Here are some common reasons why they are used:

1. Time Efficiency Performing regular full backups can be time-consuming, especially when dealing with large amounts of data. Differential backups help save time by capturing only the changes since the last full backup. This reduces the overall backup duration and minimizes the impact on system performance.
2. Storage Efficiency Since differential backups only include the changed data since the last full backup, they require less storage space compared to full backups. This can be especially beneficial when dealing with limited storage resources or when backing up large amounts of data over a network.
3. Faster Restores When it comes to data restoration, using differential backups can speed up the process. To restore data, you only need the most recent full backup and the latest differential backup. This means you don’t have to restore multiple incremental backups in sequence to reach the desired recovery point.
4. Point-in-Time Recovery By combining the most recent full backup with the latest differential backup, you can restore your data to a specific point in time. This can be useful in scenarios where you want to recover data to a known state, such as before a specific event or data corruption occurred.
5. Simplicity Differential backups offer a straightforward backup approach. They are easy to understand and implement, making them suitable for individuals or organizations without complex backup requirements or specialized IT expertise.

However, it’s important to consider the limitations of differential backups. As more differential backups accumulate, the size of the backups grows, and backup durations increase accordingly. Additionally, the dependency on previous backups means that if any differential backup in the chain is lost or corrupted, subsequent differential backups relying on it may become unusable. Therefore, it’s essential to regularly validate and test the integrity of the backup chain to ensure data recoverability

Differential Backup vs. Incremental Backup

Differential backup and incremental backup are two different methods used in data backup strategies. While they both aim to optimize backup efficiency by capturing only changed data, there are some key differences between them:

Differential Backup

• A differential backup captures all the changes made since the last full backup, regardless of previous differential backups.
• Each differential backup accumulates all the changes made up to that point, resulting in larger backup sizes as time passes.
• Restoring data requires the most recent full backup and the latest differential backup.
• Differential backups are faster to create than full backups but slower than incremental backups since they capture more data.
• The backup process is relatively simple and easy to understand.

Incremental Backup

• An incremental backup captures only the changes made since the last backup, whether it was a full backup or an incremental backup.
• Each incremental backup contains only the changes since the last backup, resulting in smaller backup sizes and shorter backup durations over time.
• Restoring data requires the most recent full backup and all the incremental backups performed since that full backup.
• Incremental backups are faster to create than both full and differential backups since they capture only the changed data since the last backup.
• The backup process can be more complex, especially when multiple incremental backups need to be applied during the restoration process.

Choosing between differential and incremental backups depends on factors such as data size, available storage resources, backup and restore time requirements, and data recovery objectives. Here are some considerations:

• Differential backups are suitable when you prefer faster restores as they require only the last full backup and the latest differential backup.
• Incremental backups are ideal when you want to optimize storage space and backup durations since they capture only the changed data since the last backup, regardless of backup type.
• Incremental backups may require more effort and time during the restoration process since you need to apply multiple incremental backups in the correct order.

Ultimately, the best backup strategy may involve a combination of full, differential, and incremental backups, tailored to the specific needs and constraints of the data and system being protected.

What a differential backup does during a backup

During a backup, a differential backup performs the following steps:

• Identifies Changed Data The differential backup software examines the source system’s files and folders to determine which data has changed since the last full backup. This can be done by comparing attributes, timestamps, or content of the files against the information recorded during the full backup.
• Selects Changed Data Once the changes are identified, the differential backup selects the files and folders that have been modified or added since the last full backup. These are the specific data elements that will be included in the current differential backup.
• Copies Changed Data The selected changed files and folders are copied from the source system to the backup destination. Only the modified or newly added data is transferred during this process. Unchanged files from the previous full backup are not included in the differential backup to avoid duplication.
• Updates Backup Catalog The backup software updates the backup catalog or index, which keeps track of the backup chain and the changes captured in each differential backup. This catalog helps in managing and organizing the backup sets for future restoration purposes.
• Completes the Backup Once the changed data has been copied and the backup catalog is updated, the differential backup process is completed. The resulting differential backup represents all the changes made since the last full backup, forming a new point in the backup chain.

How to select the best backup for your use case

Selecting the best backup strategy for your use case involves considering several factors and evaluating your specific needs and constraints. Begin by assessing the nature of your data, taking into account its size, growth rate, criticality, and sensitivity. Identify any regulatory or compliance requirements that may influence your backup strategy. Next, define your recovery objectives, including recovery time objectives (RTO) and recovery point objectives (RPO). RTO refers to the maximum acceptable downtime, while RPO defines the maximum tolerable data loss. These objectives will guide your backup strategy decisions.

Evaluate the different backup methods available, such as full backup, differential backup, and incremental backup. Consider the advantages and disadvantages of each method, including backup speed, storage efficiency, and restore time. Assess your available storage resources, including capacity and scalability. Determine whether you have sufficient storage for full backups or if you need to optimize space using differential or incremental backups.

Assess the backup frequency based on your recovery objectives and the rate of data change. Critical systems may require more frequent backups, while less critical data may be backed up less often. Consider the restoration process and the time it takes to restore data from different backup methods. Evaluate the complexity and reliability of restoring data from full backups, differential backups, and incremental backups.

Regularly test and validate your backup strategy to ensure its effectiveness. Perform restoration tests to verify the recoverability of your data and evaluate the performance of your chosen backup method. Explore backup solutions that offer automation and monitoring capabilities. Automated backups can streamline the process, while monitoring tools provide visibility into the status and health of your backups.

If you are uncertain about the best backup strategy for your use case, seek advice from IT professionals, backup solution providers, or data management experts. They can provide insights and recommendations based on their expertise. Remember that backup strategies are not one-size-fits-all and may need to be adjusted over time to align with your evolving requirements and the technology landscape. Regularly review and update your backup strategy to ensure it provides the necessary data protection for your specific needs.

Differential Backup In your network

From a network administrator’s perspective, implementing a differential backup strategy provides the advantages of reducing network traffic and faster backup speeds. With differential backups, only the changed data since the last full backup is transmitted over the network, minimizing bandwidth consumption and the impact on other network operations.

In addition, this approach allows for quicker backup completion compared to performing full backups each time, improving overall backup efficiency and minimizing potential disruptions to network performance.