The monitor checks latency for the disk write operation and throws an alert.
This alert indicates that the average time that it takes to write on the disk has stayed greater than threshold during an interval.
The problem may be caused by low performance of the Microsoft SQL Server or by a disk bottleneck.
To resolve this error, do one or more of the following:
Determine if disk performance has degraded or workload has increased.
Evaluate SQL Server Storage Best practices.
Determine if storage for database files has been overcommitted e.g. shared storage in SAN or Virtual Machines.
Verify an adequate amount of memory has been allocated to SQL. SQL server memory starvation can result in higher than normal physical reads.
SQL Server Best Practices Article (Disk Configuration Best Practices & Common Pitfalls)