[ENT-1567] Document hot-cold deployment

docs/source/corda-nodes-index.rst

@@ -12,4 +12,5 @@ Corda nodes
    shell
    node-database
    node-administration
-   out-of-process-verification
+   out-of-process-verification
+   high-availability

docs/source/high-availablility.rst

@@ -0,0 +1,48 @@
+High Availability
+=================
+
+This section describes how to make a Corda node highly available.
+
+Hot Cold
+~~~~~~~~
+
+In the hot cold configuration, failover is handled manually, by promoting the cold node after the former hot node
+failed or was taken offline for maintainance.
+
+RPC clients have to handle ``RPCException`` and implement application specific recovery and retry.
+
+Prerequisites
+-------------
+
+* A load-balancer for P2P, RPC and web traffic
+* A shared file system for the artemis and certificates directories
+* A shared database, e.g. Azure SQL
+
+The hot-cold deployment consists of two Corda nodes, a hot node that is currently handling request and running flows
+and a cold backup node that can take over, if the hot node fails or is taken offline for an upgrade. Both nodes should
+be able to connect to a shared database and a replicated file-system hosting the artemis and certificates directories.
+The hot-cold ensemble should be fronted by a load-balancer for P2P, web and RPC traffic. The load-balancer should do
+health monitoring and route the traffic to the node that is currently active. To prevent data corruption in case of
+accidental simultaneous start of both nodes, the current hot node takes a leader lease in the form of a mutual exclusion
+lock implemented by a row in the shared database.
+
+Configuration
+-------------
+
+The configuration snippet below shows the relevant settings.
+
+.. sourcecode:: none
+
+    enterpriseConfiguration = {
+        mutualExclusionConfiguration = {
+            on = true
+            machineName = ${HOSTNAME}
+            updateInterval = 20000
+            waitInterval = 40000
+        }
+    }
+
+Hot Warm
+~~~~~~~~
+
+In the future we are going to support automatic failover.