SQL Server Backup and Recovery

Backup Types

When it comes to backing up databases, there are three main types of backups: Full, Differential, and Transaction Log. It is important to understand each of them in order to create an effective backup plan.

• Full Backup is the backup of an entire database. It can be performed for all databases and it’s the foundation of every backup plan. Full backups are usually performed on a regular basis, depending on the size and complexity of the database. Full backups allow you to recover an entire database in case of data loss.

• Differential Backup is the backup of any changes that have been made since the last Full Backup. Differential backups are smaller in size and quicker to perform than full backups. They are useful in reducing the backup time and space required for storing backups. Differential backups allow you to restore a database to a specific point in time.

• Transaction Log Backup is the backup of all transactions that have occurred since the last Transaction Log Backup or Full Backup. Transaction Log backups are used to recover a database to a specific point in time, just like Differential backups. Transaction Log backups are also used to minimize the amount of data loss in case of a disaster. It is recommended to take Transaction Log backups frequently when critical data is involved.

In order to create an effective backup plan, you would want to combine the different types of backups. For example, perform a Full Backup once a week, Differential backups once a day, and Transaction Log backups every hour.

SQL Server Management Studio (SSMS) allows you to schedule backups to run at specific times using the SQL Server Agent. You can also use T-SQL to create backups scripts, automate and customize, and save them to run as jobs.

--Full backup
BACKUP DATABASE [DatabaseName] TO DISK = 'C:\Backup\DatabaseName_Full.bak'

--Differential backup
BACKUP DATABASE [DatabaseName] TO DISK = 'C:\Backup\DatabaseName_Diff.bak' WITH DIFFERENTIAL

--Transaction log backup
BACKUP LOG [DatabaseName] TO DISK = 'C:\Backup\DatabaseName_Log.bak'

It is important to regularly test your backup plan by restoring a backup to a test environment. This helps to ensure that you can recover your critical data, in case of data loss.

In conclusion, a good backup plan is an essential component of a disaster recovery strategy. Understanding the different types of backups and scheduling them appropriately can help minimize data loss and ensure quick recovery time.

Recovery Models

SQL Server provides different recovery models to help protect against data loss. The three recovery models are Simple, Full, and Bulk-Logged. Each model defines the amount of data that will be backed up and how much data loss can occur in case of a disaster. It’s important to select the correct recovery model based on the needs of the database.

• Simple Recovery Model is the most basic recovery model. It allows for minimal logging and only information needed to recover the transaction that is currently running. In Simple Model, every checkpoint truncates the transaction log making the space available for new transactions. This model is best used for non-production databases, or low-volume data warehouses where you can afford to lose data in a disaster scenario before the next backup. Since transaction logs are frequently truncated, Simple Model provides the least amount of data protection.

• Full Recovery Model provides complete data recoverability. The Full Model ensures that all transactions are logged, and the transaction logs are useful in disaster recovery scenarios. This model takes full, differential, and log backups. Full backups are essential in restoring a database while Differential and Log backups help to restore the data from the last backup. Having a full backup with proper log backups helps to recover the database to a specific point in time. Full model is recommended for production databases or high-transactional databases where data loss is unacceptable.

• Bulk Logged Recovery Model is best used for large database operations such as bulk loads of data. This model minimizes the amount of logging performed on large scale operations. Similar to Full Model, Bulk-Logged Model supports full and differential backups. However, transaction logs in this model are only partially logged during bulk operations, making log backups minimal. After the completion of the bulk operation, we can take a full or differential backup.

You can easily switch between recovery models using SQL Server Management Studio user interface or using T-SQL.

--Switch recovery model from Simple to Full
ALTER DATABASE [DatabaseName] SET RECOVERY FULL

--Switch recovery model from Full to Simple
ALTER DATABASE [DatabaseName] SET RECOVERY SIMPLE

In conclusion, a recovery model is a critical component of a disaster recovery strategy. It’s important to choose the right model and to schedule and perform backups in the way that matches with the recovery model you’ve chosen.

Backup Strategies

A backup strategy is a comprehensive plan that outlines when and how backups will be taken to ensure data protection and recovery in case of data loss scenarios. A good backup strategy must consider backup frequency, backup storage, backup validation, and backup retention policies.

• Backup Frequency defines how frequently backups should be performed. The frequency is usually determined by the Recovery Point Objective (RPO) — a measurement of how much data loss is acceptable. For example, in mission-critical systems, frequent backups are required to minimize the amount of data loss in case of a disaster scenario, while in a test environment, frequent backups may not be necessary.

• Backup Storage determines where and how backups will be stored. Backup files should be kept in a secure location that is separate from the production environment. The backups can either be stored on tapes, network shares, or cloud storage. You should ensure that the backup location is scalable and easily accessible when needed.

• Backup Validation is a process of verifying that the backup files are valid and restorable. Validating backups includes performing test restorations in a sandbox environment, checking backup logs for warnings and errors, and ensuring that the backup files can be accessed.

• Retention Policies define how long backup files will be kept. Retention policies should consider various factors such as the legal requirements, backup storage space, and the RPO. It’s important to ensure that the retention period is sufficient for restoring data up to the required point in time.

In addition to the backup strategies mentioned above, it’s also important to plan for disaster recovery scenarios. A database disaster recovery strategy should include documentation of the procedures such as how to identify the disaster recovery team, how to activate the backup plan, and how to align people, processes, and technology. Disaster recovery strategy should be tested regularly to ensure they work effectively.

SQL Server provides various mechanisms and tools for implementing robust backup strategies. SQL Server Agent is a built-in tool that allows scheduling backup jobs at specified intervals using the many scheduling options available. Additionally, you can use SQL Server Integration Services (SSIS) to automate complex backup scenarios.

In conclusion, a backup strategy is essential to protect against data loss scenarios. A comprehensive backup strategy that includes frequency, storage, validation, and retention policies, along with a well-documented disaster recovery plan, can ensure that your critical data is recoverable in the case of an unforeseen data loss scenario.

Test Your Restore Process

Having a well-designed backup plan is great, but it’s equally important to ensure the backups can be restored. With today’s databases becoming more and more complex, it is crucial to regularly test your restore process. You do not want to wait until a disaster occurs to find out that your backups are invalid, corrupt or incomplete.

Testing your restore process involves validating that your backup files are functional and that you can restore them successfully in a disaster scenario. The testing should be done in a test environment and not in the production environment.

To test your restore process, you should do the following:

1. Restore both Full and Log backups in the sandbox environment: Test restoring the backups to the same point in time so that you can validate that your transaction logs are consistent with your backup data.

2. Check the error log: Check the SQL Server error log for any potential issues that may have occurred during the restore process.

3. Verify data integrity: After the restore process is complete, you should compare tables and indexes from the production environment against those in the test environment. This will verify that the restored data is intact and usable.

4. Test applications: After data comparison and verification, you should test end-to-end functionality of the applications in the test environment. This will ensure that the applications are usable and functional after a disaster.

5. Update your backup plan: Update the backup plan with any updates discovered during the testing process.

SQL Server provides various mechanisms for testing backup and restore process, such as Automated Restore Testing (ART) and the Microsoft Data Migration Assistant (DMA). ART allows for automated testing of backups and restores while DMA is a free tool that allows you to assess, right-size, and migrate your on-premises databases to Azure.

--Restore Full backup
RESTORE DATABASE [DatabaseName] FROM DISK = 'C:\Backup\DatabaseName_Full.bak' WITH REPLACE

--Restore Transaction log backup
RESTORE LOG [DatabaseName] FROM DISK = 'C:\Backup\DatabaseName_Log.bak' WITH NORECOVERY

In conclusion, testing your restore process is crucial to ensure that your backups can be restored in the case of a disaster. A well-designed backup plan, combined with a tested restore process, can help you minimize downtime and ensure that your data is recoverable.

Summary

Learn how to create an effective backup plan, understand the importance of the different types of backups, and discover tips and tricks to help you ensure data protection and recovery in case of data loss scenarios.

In this article, we covered the three types of backups: Full, Differential, and Transaction Log, and how each type can be used in disaster recovery scenarios. We also explored the recovery models, backup strategies, and testing your restore process.

Remember, having a robust backup plan is essential, but equally important is testing the restore process to ensure that your backups can be restored when needed.

Ensure critical data protection by having the right backup and restore process in place, and always test and update the process regularly.