Understanding SQL Server Backup Compression – ZSTD, Advantages, and Best Practices

SQL Server databases are crucial for storing business data and information. However, as the data grows, the backup files consume significant storage. To manage these backups, database administrators prefer using SQL Server backup compression to handle a large volume of data effectively. With the help of this blog, we will learn more about these compressed backups and how they work. 

What is SQL Server Backup Compression? Brief Overview

Compression in SQL Server is a feature that reduces the size of database backup files. When a user backs up a database without using compression, the SQL Server engine writes the backup data to the designated destination in a regular backup format. When backup compression is enabled, the backup is compressed before being written to the destination. The compressed backup is supported in SQL Server 2008 R2, 2012, 2014, 2016, 2017, 2019, 2022 and 2025 versions. 

This is the basic explanation of backup compression in the database. Now, to understand this more clearly, it is important for the users to understand the working of backup compression. Let’s go through how SQL Server backup compression works. 

How does SQL Compressed Backup Work?

This backup process works by minimizing the repetitive patterns within the backup data. 

Below are the steps followed by compressed backups:

1. The SQL Server engine reads the database pages first for the backup process. 
2. Next, the backup process identifies the data to be compressed. 
3. Then, the compression algorithm is applied to the specified data. 
4. The compressed backup is written to the destination. 
5. Lastly, when the compressed backup is required, SQL Server decompresses the backup data automatically. 

These are the steps carried out for the SQL Server backup compression process. The compression process generally occurs at the time of backup creation; hence, SQL Server uses additional CPU resources to reduce the data written to storage. As we are now aware of the process, let’s take a look at the importance of the process in SQL Server. 

Benefits of SQL Compressed Backups Explained

We will now understand the benefits of these backups in SQL Server:

• Helps save storage space by minimizing the backup file sizes. 
• Makes it simpler for users to store and manage data.
• Minimizes the time required for the backup transfer. 
• Allows users to speed up the backup operations in required environments.
• Helps database administrators store more backups in the same storage space. 
• Helps simplify backup management for larger databases in SQL Server. 

Here are the advantages of compressed SQL backups. Now we will take a look at the methods for enabling backup compression. 

How to Enable SQL Server Backup Compression? All Methods Listed

SQL Server databases offer multiple ways to enable backup compression. We will go through these methods one by one and understand how they work. 

Method 1: Compress Backup Using T-SQL Queries

One of the methods to enable backup compression in SQL Server is by using the T-SQL command. Below are the steps on how one can carry out the process. 

Step 1: Open SQL Server Management Studio. Connect it to the SQL Server instance. 

Step 2: In a New Query Window, execute the following command:

BACKUP DATABASE [Database_Name]
TO DISK = 'D:\SQLBackups\Database_Name_Compressed.bak'
WITH COMPRESSION,
     INIT,
     STATS = 10;

Step 3: SQL Server starts executing the backup compression operation and reduces the backup file size before writing it to the destination. 

The COMPRESSION command explicitly enables the compression operation in the database. Let’s now take a look at the next method for SQL Server backup compression. 

Method 2: Use SSMS for Backup Compression in SQL Server

Here are the steps on how users can implement compression in SQL Server backups using SQL Server Management Studio.

1. Open SSMS and connect to the SQL Server instance. 
2. Expand the Databases section, and then right-click on the required database. 
3. Go to the Tasks option and then choose the Backup Option. 
4. Choose the required backup type from Full, Differential, or Transaction Log Backup. 
5. Next, add the backup destination under the Destination section to save the database backups. 
6. Then, go to the Backup Options Page. Choose Compress Backup under the Compression Section.
7. Verify other required backup settings and configuration settings, then click the OK button. 

This method helps users take compressed backups in SQL Server without needing complex code. This is a method that can help database administrators with the compression process. As we discussed earlier, compressed backups are supported in all versions after SQL Server 2008. Hence, the latest SQL version, i.e., SQL Server 2025, also supports compressed backups. 

In the latest SQL version, Microsoft has introduced the ZSTD Algorithm for backup compression. Let’s now understand what it is and how it is different from the legacy compression mechanisms.

BACKUP DATABASE [Database_Name]
TO DISK = 'D:\SQLBackups\Database_Name_ZSTD.bak'
WITH COMPRESSION (ALGORITHM = ZSTD);

Factors Affecting SQL Server Backup Compression Process

There are various factors that might affect the compression process with SQL Server backups. We will take a look at them one by one for a clearer understanding.

• One of the factors affecting backup compression in SQL Server is the type of database being used. 
• If backup compression is already enabled, it may provide limited additional savings. 
• Encrypted databases are often more difficult to compress, as the encryption in the database removes many repetitive patterns that are crucial for compression algorithms. 
• For backup compression, CPU resources are required. Therefore, if there are other operations using CPU resources, the compression might end up competing with other operations, further affecting overall database performance. 

These are some of the factors that affect the overall performance of SQL Server and backup compression altogether. We will now take a look at the safety measures that will allow users to carry out the compression process seamlessly. 

Best Practices for SQL Server Backup Compression

• The first step is to evaluate the environment. This can be done by testing compression on specific databases, instead of the complete environment.
• It is important to monitor the CPU usage during the compression process to detect performance bottlenecks.
• Ensure that the compressed backups can be restored within the specified recovery time objective (RTO).
• Use appropriate schedules for backup compression, such as during maintenance windows, to prevent downtime. 
• Before database backup compression, check whether the target server version supports the compression algorithm or not. 

Conclusion

With the help of this blog, we have learned about SQL Server backup compression and how it is beneficial to users. We have also listed how it works, methods to enable compression, and what factors affect the compression process. Lastly, we have also suggested best practices to ensure the process is carried out efficiently.

Frequently Asked Questions About Compressed BAK Files in SQL Server

Q1. Does backup compression affect the integrity of the database?

Ans. No. Backup compression doesn’t affect data integrity. Moreover, the data is restored exactly as it was when the backup was taken. The compression process only reduces the size of the backup file. 

Q2. Does the compression process work on databases that are encrypted?

Ans. Yes. Backup compression works effectively on encrypted databases, but the size reduction of the backup files is generally smaller. 

Q3. Is it required to enable backup compression for every database?

Ans. Except for databases that are encrypted or already compressed, it is usually good practice to compress every database in a SQL Server environment.