Understanding SQL Server VSS Writer: A Comprehensive Guide for Devs

Dear Dev, if you work in IT and have anything to do with SQL Server, then you are probably familiar with the term VSS writer. But do you know what it actually means and what role it plays in your daily work? In this article, we will take a deep dive into SQL Server VSS writer, its functions, and how you can optimize its performance. So, let’s get started!

What is SQL Server VSS Writer?

The Volume Shadow Copy Service (VSS) is a Microsoft technology included in Windows Server that allows you to create point-in-time copies (shadow copies) of one or more volumes. These shadow copies can be used for backup and recovery purposes, as well as for creating snapshot-based backups of virtual machines. SQL Server VSS writer is an important component of the VSS technology, which enables consistent application-aware backups of SQL Server databases.

So how does it work? Basically, SQL Server VSS writer is a module that runs within the SQL Server process and communicates with the VSS service to create and maintain the shadow copies of the SQL Server databases. When a VSS backup is initiated, the SQL Server VSS writer is called upon to prepare the database for backup by coordinating with other SQL Server components, such as the transaction log and buffer cache. It then notifies the VSS service to create a shadow copy of the volume containing the database files, which can be used by backup software to create a consistent backup of the database.

How does SQL Server VSS Writer differ from other backup methods?

There are several methods for backing up SQL Server databases, including full, differential, and transaction log backups. While each of these methods has its own advantages and disadvantages, they all have one thing in common: they require the database to be taken offline or put into a special mode that prevents data modifications during the backup operation. This can result in downtime for your application and may not be feasible for 24/7 environments.

SQL Server VSS writer, on the other hand, allows you to perform backups without taking the database offline or disrupting normal operation. It achieves this by creating a consistent snapshot of the database, which can be used to create a backup that reflects the state of the database at the time the snapshot was taken. This enables you to perform backups at any time, without affecting the performance or availability of your applications.

How to Configure SQL Server VSS Writer?

Now that you know what SQL Server VSS writer is and how it works, let’s look at how you can configure it for your environment. There are several steps you need to follow to ensure that SQL Server VSS writer is correctly configured and optimized for performance. These steps include:

Step 1: Verify that VSS is installed and running

If you don’t see the SQL Server VSS writer listed in the output of these commands, it may not be installed or properly registered on the system. You can try reinstalling SQL Server or running the following command to register the VSS writer manually:

regsvr32.exe sqlvdi.dll

Step 2: Verify that the SQL Server VSS Writer service is running

SQL Server VSS writer is implemented as a Windows service named SQL Server VSS Writer. You can check whether it’s running by opening the Services console (services.msc) and looking for the service named SQL Server VSS Writer. If the service is not running, you can start it manually or configure it to start automatically.

Step 3: Configure SQL Server VSS Writer Options

You can configure SQL Server VSS Writer options using the SQL Server Management Studio (SSMS) or T-SQL commands. The most commonly used options are:

Step 4: Test SQL Server VSS Writer

Before you start relying on SQL Server VSS writer for your backups, it’s important to test it thoroughly to make sure that it’s working as expected. You can do this by creating a test backup job and checking the backup file for consistency.

FAQs about SQL Server VSS Writer

Q: What versions of SQL Server support VSS writer?

A: SQL Server 2005 and later versions support VSS writer.

Q: Can I use SQL Server VSS writer for log backups?

A: No, SQL Server VSS writer is not designed for log backups. You should use the native SQL Server log backup functionality for this purpose.

Q: Are there any performance implications of using SQL Server VSS writer?

A: Yes, there may be some performance overhead associated with using SQL Server VSS writer, especially if you’re backing up large databases or running on an older operating system. However, this overhead is typically much lower than the downtime required for other backup methods.

Q: How does SQL Server VSS writer handle database corruption?

A: If the SQL Server VSS writer detects a corrupted database during a backup operation, it will notify the backup software and the backup will fail. You can use the SQL Server Database Console Commands (DBCC) to repair the database and try the backup again.

Q: Can I use SQL Server VSS writer with third-party backup software?

A: Yes, SQL Server VSS writer is compatible with most third-party backup software that supports VSS technology.

Q: Is it recommended to use SQL Server VSS writer for production backups?

A: Yes, SQL Server VSS writer is a reliable and efficient method for backing up SQL Server databases, and is recommended for production use.

Conclusion

SQL Server VSS writer is an important component of the VSS technology, which enables consistent application-aware backups of SQL Server databases. By allowing you to perform backups without taking the database offline or disrupting normal operation, SQL Server VSS writer can reduce downtime and improve the availability of your applications. By following the configuration and performance tuning tips outlined in this article, you can ensure that SQL Server VSS writer is optimized for your environment and providing the best possible backup performance.