Certain versions of supported Linux distributions provide support for FUA I/O subsystem capability, which provides data durability. [!INCLUDE ssnoversion-md] uses FUA capability to provide highly efficient and reliable I/O for [!INCLUDE ssnoversion-md] workloads. For more information on FUA support by Linux distribution and its effect on [!INCLUDE ssnoversion-md], see SQL Server On Linux: Forced Unit Access (FUA) Internals.

SUSE Linux Enterprise Server 12 SP5, Red Hat Enterprise Linux 8.0, and Ubuntu 18.04 introduced support for FUA capability in the I/O subsystem. If you're using [!INCLUDE sssql17-md] CU 6 and later versions, you should use following configuration for high performing and efficient I/O implementation with FUA by [!INCLUDE ssnoversion-md].

Use this recommended configuration if the following conditions are met.

• Using [!INCLUDE sssql17-md] CU 6 and later versions
• Using a Linux distribution and version that supports FUA capability (starting with Red Hat Enterprise Linux 8.0, SUSE Linux Enterprise Server 12 SP5, or Ubuntu 18.04)
• On storage subsystem and/or hardware that supports and is configured for FUA capability

Recommended configuration:

1. Enable Trace Flag 3979 as a startup parameter
2. Use mssql-conf to configure control.writethrough = 1 and control.alternatewritethrough = 0

For almost all other configuration that doesn't meet the previous conditions, the recommended configuration is as follows:

1. Enable Trace Flag 3982 as a startup parameter (which is the default for [!INCLUDE ssnoversion-md] in the Linux ecosystem), and make sure that Trace Flag 3979 isn't enabled as a startup parameter
2. Use mssql-conf to configure control.writethrough = 1 and control.alternatewritethrough = 1