Add more explanation to options

Signed-off-by: Pavol Loffay <[email protected]>

plugin/storage/es/options.go

@@ -194,7 +194,9 @@ func addFlags(flagSet *flag.FlagSet, nsConfig *namespaceConfig) {
 		flagSet.Bool(
 			nsConfig.namespace+suffixReadAlias,
 			nsConfig.UseReadWriteAliases,
-			"Use read and write aliases for indices. Use this option with rollover API. It requires to create aliases before startup.")
+			"Use read and write aliases for indices. Use this option with Elasticsearch rollover "+
+				"API. It requires an external component to create aliases before startup and then performing its management. "+
+				"Note that "+nsConfig.namespace+suffixMaxSpanAge+" is not taken into the account and has to be substituted by external component managing read alias.")
 	}
 }