Add notes on deleting seed nodes

Author: peterpogorski

articles/service-fabric/service-fabric-azure-resource-manager-guardrails.md

@@ -6,7 +6,7 @@ documentationcenter: .net
 author: peterpogorski
 
 ms.topic: conceptual
-ms.date: 10/30/2019
+ms.date: 02/13/2020
 ms.author: pepogors
 ---
 # Service Fabric guardrails 
@@ -55,12 +55,27 @@ The following section contains an example of a durability mismatch between the V
 * Virtual Machine Scale Set durability does not match the target Service Fabric Node Type durability level
 * Virtual Machine Scale Set durability does match the current Service Fabric durability level or the target Service Fabric Node Type durability level 
 
-
 ### Mitigation
 To fix a durability mismatch, which is indicated by any of the above error messages:
 1. Update the durability level in either the Virtual Machine Scale Set extension or Service Fabric Node Type section of the Azure Resource Manager template to ensure that the values match.
 2. Redeploy the Azure Resource Manager template with the updated values.
 
+
+## Seed Node Deletion 
+### Overview
+The reliability tier of a cluster is used to determine the number of replicas of system services that you would like to run on the primary node type of the cluster. See [reliability characteristics of the cluster](https://docs.microsoft.com/en-us/azure/service-fabric/service-fabric-cluster-capacity#the-reliability-characteristics-of-the-cluster). Depending on the reliability tier that is selected there must always be a minimum number of nodes in the cluster in order to run the required number of replicas. If the number of nodes in this primary node type goes below this minimum the cluster can become unstable.  
+
+### Error Messages 
+Seed node removal operation has been detected, and will be rejected. 
+* This operation would result in only {0} potential seed nodes to remain in the cluster, while {1} are needed as a minimum.
+* Removing {0} seed nodes out of {1} would result in the cluster going down due to loss of seed node quorum. Maximum number of seed nodes that can be removed at a time is {2}.
+ 
+### Mitigation 
+Make sure that the Virtual Machine Scale Set which is mapped to your primary node type has enough virtual machines for the reliability tier that is specified on your cluster. You will not be able to remove a Virtual Machine if it will bring the Virtual Machine Scale Set below the minimum number of Virtual Machines which are required for the specified reliability level. 
+* If the reliability level is correctly specified, make sure that you have enough VMs as needed for the reliability level. Make sure to add new Virtual Machines to the Virtual Machine Scale Set to add enough nodes to cover the deficit. 
+* If the reliability level is incorrect, initiate a change on the Service Fabric resource to lower reliability level first before initiating any Virtual Machine Scale Set operations, and let it complete.
+* If the reliability level is Bronze, please follow these [steps](https://docs.microsoft.com/azure/service-fabric/service-fabric-cluster-scale-up-down#manually-remove-vms-from-a-node-typevirtual-machine-scale-set) to scale down your cluster gracefully.
+
 ## Next steps
 * Create a cluster on VMs or computers running Windows Server: [Service Fabric cluster creation for Windows Server](service-fabric-cluster-creation-for-windows-server.md)
 * Create a cluster on VMs or computers running Linux: [Create a Linux cluster](service-fabric-cluster-creation-via-portal.md)