SQL Server Log Writer Workers

02/11/2019

2 minutes to read

In this article

SQL Server 2017 leverages up to 4 log writer workers, on hidden schedulers, to assist in transaction log processing activities. You may find the number of log write workers has been increased to 8 when running newer releases of SQL Server to accommodate larger systems. (Caution: Pre-release software may change before final release.)

During SQL Server startup the number of log writer workers is determined.

If multiple log write workers are not allowed use a single log writer

Otherwise

Total number NUMA nodes * 2

Count the number of available CPUs on the NUMA node (affinity mask can impact this count)

Take the smaller of the above calculations and cap by the MAX_LOG_WRITERS allowed (4 or 8 depending on version)

Bob Dorr