diff --git a/roles/nginx/files/nginx.conf b/roles/nginx/files/nginx.conf
index 85f8644..63ccdfe 100644
--- a/roles/nginx/files/nginx.conf
+++ b/roles/nginx/files/nginx.conf
@@ -23,6 +23,11 @@ http {
 
     access_log off;
 
+    # Speed up file transfers by using sendfile() to copy directly
+    # between descriptors rather than using read()/write().
+    # For performance reasons, on FreeBSD systems w/ ZFS
+    # this option should be disabled as ZFS's ARC caches
+    # frequently used files in RAM by default.
     sendfile        on;
     #tcp_nopush     on;