diff --git a/README.md b/README.md
index e2a4b44..9925467 100644
--- a/README.md
+++ b/README.md
@@ -38,6 +38,9 @@ Longhorn is 100% open source software. Project source code is spread across a nu
     1. For GKE, recommended Ubuntu as guest OS image since it contains open-iscsi already.
     2. For Debian/Ubuntu, use `apt-get install open-iscsi` to install.
     3. For RHEL/CentOS, use `yum install iscsi-initiator-utils` to install.
+4. A host filesystem supports `file extents` feature on the nodes to store the data. Currently we supports:
+    1. ext4
+    2. XFS
 
 # Install