FAQs - SQL Server and Disk Subsystem requirements

This is the first installment in my FAQ series.


In this blog entry, I have consolidated all the questions that I have received from my readers about available disk subsystems in the market and their compatibility with SQL Server.

I have tried to address them here.

Q : I have an unused NAS (Network Attached Storage). I wanted to know if SQL Server supports files located on NAS and if there are any issues that I should be aware of?

A : By default, SQL Server doesn’t support data files located on a NAS. However, trace flag 1807 overrides this behavior.

With NAS, there are special considerations for SQL Server performance that you should be aware off. Please refer to the KB 304261 for more information on this.

Q : Does Microsoft recommend SAN over NAS or vice versa for SQL Server?

A : Microsoft generally recommends that you use a Storage Area Network (SAN) or locally attached disk for the storage of your Microsoft SQL Server database files because this configuration optimizes SQL Server performance and reliability.

However, any certified NAS device can also be used with SQL Server.Please refer to the KB 304261 for more information on this.

Q : I have heard that SQL Server can be used Internet Small Computer System Interface (iSCSI). Is that true? If yes, then are there any issues that I should be aware off?

A : Yes, SQL Server can be used with iSCSI and Microsoft supports this configuration.

However, Microsoft recommends that you use special caution here. For more information on this, refer to KB 833770.

To check if your iSCSI hardware components are qualified, refer to the Microsoft iSCSI Hardware Device Qualified list here.

Q : Many third-party vendors are providing disk drive caching solutions. Can SQL Server be used in conjunction with these solutions? Are there any known issues?

A : Caching controllers and disk subsystems can be safe for use by SQL Server. However, you should check with your hardware vendor to be sure that the disk subsystem has been specifically tested and approved for use in a data critical transactional relational database management system (RDBMS) environment.

For more details, refer to KB 86903.

Also, SQL Server implements Write-Ahead Logging (WAL) which ensures data integrity and recovery.

Refer to KB 234656 article that describes SQL Server’s implementation of WAL and how it interacts with the hardware based caching solutions.


Q : What is the difference between System Area Network and Storage Area Network?

A : SAN terminology is used interchangeably for both System Area Network and Storage Area Network. However, there are differences in their implementations. Refer to KB 264135 for more details.

I will continue to update this post with more such questions. Also, let me know if you have anything on your mind that you would like me to address or cover through this blog. Thanks.