diff --git a/hadoop-common-project/hadoop-kms/src/site/markdown/index.md.vm b/hadoop-common-project/hadoop-kms/src/site/markdown/index.md.vm
index d2d1d994538..729b2b9aed8 100644
--- a/hadoop-common-project/hadoop-kms/src/site/markdown/index.md.vm
+++ b/hadoop-common-project/hadoop-kms/src/site/markdown/index.md.vm
@@ -19,6 +19,8 @@
Hadoop Key Management Server (KMS) - Documentation Sets
=======================================================
+
+
Hadoop KMS is a cryptographic key management server based on Hadoop's **KeyProvider** API.
It provides a client and a server components which communicate over HTTP using a REST API.
@@ -34,6 +36,18 @@ KMS Client Configuration
The KMS client `KeyProvider` uses the **kms** scheme, and the embedded URL must be the URL of the KMS. For example, for a KMS running on `http://localhost:16000/kms`, the KeyProvider URI is `kms://http@localhost:16000/kms`. And, for a KMS running on `https://localhost:16000/kms`, the KeyProvider URI is `kms://https@localhost:16000/kms`
+The following is an example to configure HDFS NameNode as a KMS client in
+`hdfs-site.xml`:
+
+
+ dfs.encryption.key.provider.uri
+ kms://http@localhost:9600/kms
+
+ The KeyProvider to use when interacting with encryption keys used
+ when reading and writing to an encryption zone.
+
+
+
KMS
---
@@ -623,13 +637,51 @@ Additionally, KMS delegation token secret manager can be configured with the fol
```
-$H3 Using Multiple Instances of KMS Behind a Load-Balancer or VIP
+$H3 High Availability
-KMS supports multiple KMS instances behind a load-balancer or VIP for scalability and for HA purposes.
+Multiple KMS instances may be used to provide high availability and scalability.
+Currently there are two approaches to supporting multiple KMS instances:
+running KMS instances behind a load-balancer/VIP,
+or using LoadBalancingKMSClientProvider.
-When using multiple KMS instances behind a load-balancer or VIP, requests from the same user may be handled by different KMS instances.
+In both approaches, KMS instances must be specially configured to work properly
+as a single logical service, because requests from the same client may be
+handled by different KMS instances. In particular,
+Kerberos Principals Configuration, HTTP Authentication Signature and Delegation
+Tokens require special attention.
-KMS instances behind a load-balancer or VIP must be specially configured to work properly as a single logical service.
+$H4 Behind a Load-Balancer or VIP
+
+Because KMS clients and servers communicate via a REST API over HTTP,
+Load-balancer or VIP may be used to distribute incoming traffic to achieve
+scalability and HA. In this mode, clients are unaware of multiple KMS instances
+at the server-side.
+
+$H4 Using LoadBalancingKMSClientProvider
+
+An alternative to running multiple KMS instances behind a load-balancer or VIP,
+is to use LoadBalancingKMSClientProvider. Using this approach, a KMS client
+(for example, a HDFS NameNode) is aware of multiple KMS instances, and it sends
+requests to them in a round-robin fashion. LoadBalancingKMSClientProvider is
+implicitly used when more than one URI is specified in
+`dfs.encryption.key.provider.uri`.
+
+The following example in `hdfs-site.xml` configures two KMS
+instances, `kms01.example.com` and `kms02.example.com`.
+The hostnames are separated by semi-colons, and all KMS instances must run
+on the same port.
+
+
+ dfs.encryption.key.provider.uri
+ kms://https@kms01.example.com;kms02.example.com:9600/kms
+
+ The KeyProvider to use when interacting with encryption keys used
+ when reading and writing to an encryption zone.
+
+
+
+If a request to a KMS instance fails, clients retry with the next instance. The
+request is returned as failure only if all instances fail.
$H4 HTTP Kerberos Principals Configuration