diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 181f52be67..48d8eb3309 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -600,6 +600,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-8532. Make the visibility of DFSOutputStream#streamer member variable
     to private. (Rakesh R via wang)
 
+    HDFS-8535. Clarify that dfs usage in dfsadmin -report output includes all
+    block replicas. (Eddy Xu via wang)
+
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/DFSAdmin.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/DFSAdmin.java
index 11f2c3281a..b9781897f7 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/DFSAdmin.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/DFSAdmin.java
@@ -910,9 +910,11 @@ private void printHelp(String cmd) {
       commonUsageSummary;
 
     String report ="-report [-live] [-dead] [-decommissioning]:\n" +
-      "\tReports basic filesystem information and statistics.\n" +
+      "\tReports basic filesystem information and statistics. \n" +
+      "\tThe dfs usage can be different from \"du\" usage, because it\n" +
+      "\tmeasures raw space used by replication, checksums, snapshots\n" +
+      "\tand etc. on all the DNs.\n" +
       "\tOptional flags may be used to filter the list of displayed DNs.\n";
-    
 
     String safemode = "-safemode <enter|leave|get|wait>:  Safe mode maintenance command.\n" + 
       "\t\tSafe mode is a Namenode state in which it\n" +
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSCommands.md b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSCommands.md
index 2121958dd8..fab15f873d 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSCommands.md
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSCommands.md
@@ -336,7 +336,7 @@ Usage:
 
 | COMMAND\_OPTION | Description |
 |:---- |:---- |
-| `-report` `[-live]` `[-dead]` `[-decommissioning]` | Reports basic filesystem information and statistics. Optional flags may be used to filter the list of displayed DataNodes. |
+| `-report` `[-live]` `[-dead]` `[-decommissioning]` | Reports basic filesystem information and statistics, The dfs usage can be different from "du" usage, because it measures raw space used by replication, checksums, snapshots and etc. on all the DNs. Optional flags may be used to filter the list of displayed DataNodes. |
 | `-safemode` enter\|leave\|get\|wait | Safe mode maintenance command. Safe mode is a Namenode state in which it <br/>1. does not accept changes to the name space (read-only) <br/>2. does not replicate or delete blocks. <br/>Safe mode is entered automatically at Namenode startup, and leaves safe mode automatically when the configured minimum percentage of blocks satisfies the minimum replication condition. Safe mode can also be entered manually, but then it can only be turned off manually as well. |
 | `-saveNamespace` | Save current namespace into storage directories and reset edits log. Requires safe mode. |
 | `-rollEdits` | Rolls the edit log on the active NameNode. |