diff --git a/Filer-Active-Active-cross-cluster-continuous-synchronization.md b/Filer-Active-Active-cross-cluster-continuous-synchronization.md
index 913677b..86cb968 100644
--- a/Filer-Active-Active-cross-cluster-continuous-synchronization.md
+++ b/Filer-Active-Active-cross-cluster-continuous-synchronization.md
@@ -6,7 +6,7 @@ It can run either in Active-Active mode or Active-Passive mode.
 
 # Usage
 
-From any computer that can access filer and volume servers in both SeaweedFS clusters, run this command:
+From any computer that can access filer and volume servers in both SeaweedFS clusters, run one of these commands:
 
 ```
 # synchronize each cluster
@@ -20,6 +20,8 @@ weed filer.sync -a <filer1_host>:<filer1_port> -b <filer2_host>:<filer2_port> -i
 
 ```
 
+At the beginning, it will bootstrap from the beginning of time, or resumes from the last replication checkpoint. Later, it will just run continuously and persists checkpoints periodically.
+
 ## More clusters?
 
 If there are 3 or more clusters, you can choose fully connected setup or chained setup, or more complicated topology.