diff --git a/Performance-tuning.md b/Performance-tuning.md
index 9a045b7..425f15c 100644
--- a/Performance-tuning.md
+++ b/Performance-tuning.md
@@ -14,6 +14,8 @@ Recommendations: TODO
 
 `type = multifilesystem_nolock` turns from using lock mechanism on operating system / file system level to be handled internally by "radicale"
 
+DO NOT USE on a shared filesystem in combination with a clustered "radicale" application as there is no locking synchronization currently existing between cluster members beside using lock files on filesystem.
+
 ### max_sync_token_age
 
 Default is 30 days