Adds prereq section to changing hardware speed tolerance

Author: Steven Smith

modules/etcd-tuning-parameters.adoc

@@ -20,6 +20,9 @@ include::snippets/technology-preview.adoc[]
 
 To change the hardware speed tolerance for etcd, complete the following steps.
 
+.Prerequisites
+* You have edited the cluster instance to enable Technology Preview features. For more information, see "Understanding feature gates".
+
 .Procedure
 
 . Check to see what the current value is by entering the following command:

scalability_and_performance/recommended-performance-scale-practices/recommended-etcd-practices.adoc

@@ -24,3 +24,7 @@ include::modules/move-etcd-different-disk.adoc[leveloffset=+1]
 include::modules/etcd-defrag.adoc[leveloffset=+1]
 
 include::modules/etcd-tuning-parameters.adoc[leveloffset=+1]
+
+[role="_additional-resources"]
+.Additional resources
+xref:../../nodes/clusters/nodes-cluster-enabling-features.adoc#nodes-cluster-enabling-features-about_nodes-cluster-enabling[Understanding feature gates]