diff --git a/controller/monitor/disk_utils.go b/controller/monitor/disk_utils.go
index 8478fd035b..a833ddb235 100644
--- a/controller/monitor/disk_utils.go
+++ b/controller/monitor/disk_utils.go
@@ -21,7 +21,7 @@ import (
 )
 
 const (
-	defaultBlockSize = 4096
+	defaultBlockSize = 512
 )
 
 // GetDiskStat returns the disk stat of the given directory