DOCS-9158: set readahead to 0 for WiredTiger

source/administration/production-checklist-operations.txt

@@ -183,13 +183,19 @@ Linux
    - :ref:`Adjust the readahead settings <readahead>` on the devices
      storing your database files to suit your use case.
 
-     For the MMAPv1 storage engine, if your working
-     set is bigger that the available RAM, and the document access
-     pattern is random, consider lowering the readahead to 32 or 16.
-     Evaluate different settings to find an optimal value that maximizes
-     the resident memory and lowers the number of page faults.
-
-     For the WiredTiger storage engine, set readahead to 0 or 16.
+     - For the MMAPv1 storage engine, if your working set is bigger that the
+       available RAM, and the document access pattern is random, consider
+       lowering the readahead to 32 or 16. Evaluate different settings to find
+       an optimal value that maximizes the resident memory and lowers the
+       number of page faults.
+
+     - For the WiredTiger storage engine, set readahead to 0 regardless of
+       storage media type (spinning, SSD, etc.). In
+       general, use the recommended readahead setting unless testing shows a
+       measurable, repeatable, and reliable benefit in a higher readahead
+       value. `MongoDB Professional Support
+       <https://www.mongodb.com/products/enterprise-grade-support>`_ can
+       provide advice and guidance on non-zero readahead configurations.
 
    - Disable the ``tuned`` tool if you are running RHEL 7 / CentOS 7 in a
      virtual environment.

source/administration/production-notes.txt

@@ -592,11 +592,19 @@ consider the following recommendations:
 
 For the **WiredTiger** storage engine:
 
-- Set the readahead setting to 0 or 16. Setting a higher readahead
-  benefits sequential I/O operations. However, since MongoDB disk
-  access patterns are generally random, setting a higher readahead
-  provides limited benefit. As such, for most workloads, a readahead of
-  0 or 16 provides optimal MongoDB performance.
+- Set the readahead setting to 0 regardless of storage media type (spinning,
+  SSD, etc.). 
+
+  Setting a higher readahead benefits sequential I/O operations. However,
+  since MongoDB disk access patterns are generally random, setting a higher
+  readahead provides limited benefit or performance degradation. As such, for
+  most workloads, a readahead of 0 provides optimal MongoDB performance.
+
+  In general, set the readahead setting to 0 unless testing shows a
+  measurable, repeatable, and reliable benefit in a higher readahead value.
+  `MongoDB Professional Support
+  <https://www.mongodb.com/products/enterprise-grade-support>`_ can provide
+  advice and guidance on non-zero readahead configurations.
 
 For the **MMAPv1** storage engine: