HDFS-11033. Add documents for native raw erasure coder in XOR codes. Contributed by SammiChen.

hadoop-common-project/hadoop-common/src/main/resources/core-default.xml

@@ -647,7 +647,27 @@
   <name>io.erasurecode.codec.rs-default.rawcoder</name>
   <value>org.apache.hadoop.io.erasurecode.rawcoder.RSRawErasureCoderFactory</value>
   <description>
-    Raw coder implementation for the rs-default codec.
+    Raw coder implementation for the rs-default codec. The default value is a
+    pure Java implementation. There is also a native implementation. Its value
+    is org.apache.hadoop.io.erasurecode.rawcoder.NativeRSRawErasureCoderFactory.
+  </description>
+</property>
+
+<property>
+  <name>io.erasurecode.codec.rs-legacy.rawcoder</name>
+  <value>org.apache.hadoop.io.erasurecode.rawcoder.RSRawErasureCoderFactoryLegacy</value>
+  <description>
+    Raw coder implementation for the rs-legacy codec.
+  </description>
+</property>
+
+<property>
+  <name>io.erasurecode.codec.xor.rawcoder</name>
+  <value>org.apache.hadoop.io.erasurecode.rawcoder.XORRawErasureCoderFactory</value>
+  <description>
+    Raw coder implementation for the xor codec. The default value is a pure Java
+    implementation. There is also a native implementation. Its value is
+    org.apache.hadoop.io.erasurecode.rawcoder.NativeXORRawErasureCoderFactory.
   </description>
 </property>
 

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSErasureCoding.md

@@ -102,7 +102,7 @@ Deployment
   `io.erasurecode.codec.rs-default.rawcoder` for the default RS codec,
   `io.erasurecode.codec.rs-legacy.rawcoder` for the legacy RS codec,
   `io.erasurecode.codec.xor.rawcoder` for the XOR codec.
-  The default implementations for all of these codecs are pure Java. For default RS codec, there is also a native implementation which leverages Intel ISA-L library to improve the encoding and decoding calculation. Please refer to section "Enable Intel ISA-L" for more detail information.
+  The default implementations for all of these codecs are pure Java. For default RS codec, there is also a native implementation which leverages Intel ISA-L library to improve the performance of codec. For XOR codec, a native implementation which leverages Intel ISA-L library to improve the performance of codec is also supported. Please refer to section "Enable Intel ISA-L" for more detail information.
 
   Erasure coding background recovery work on the DataNodes can also be tuned via the following configuration parameters:
 
@@ -119,6 +119,8 @@ Deployment
 
   To check ISA-L library enable state, try "Hadoop checknative" command. It will tell you if ISA-L library is enabled or not.
 
+  It also requires three steps to enable the native implementation of XOR codec. The first two steps are the same as the above step 1 and step 2. In step 3, configure the `io.erasurecode.codec.xor.rawcoder` key with `org.apache.hadoop.io.erasurecode.rawcoder.NativeXORRawErasureCoderFactory` on both HDFS client and DataNodes.
+
 ### Administrative commands
 
   HDFS provides an `erasurecode` subcommand to perform administrative commands related to erasure coding.