Merge pull request #226228 from vamckMS/adh-autoreplace-host

Added host service healing and related commands

Author: prmerger-automator[bot]

articles/virtual-machines/dedicated-host-retirement.md

@@ -66,9 +66,9 @@ A:
 
 A: You'll need to [exchange your reservation](../cost-management-billing/reservations/exchange-and-refund-azure-reservations.md#how-to-exchange-or-refund-an-existing-reservation) through the Azure portal to match the new Dedicated Host SKU. 
 
-### Q: What would happen if I do not migrate by March 31, 2023?
+### Q: What would happen to my host if I do not migrate by March 31, 2023?
 
-A: After March 31, 2023 any dedicated hosts running the SKUs that are marked for retirement will be pushed to 'Host Pending Deallocate' before eventually deallocating the host. For additional assistance please reach out to Azure support.
+A: After March 31, 2023 any dedicated host running on the SKUs that are marked for retirement will be set to 'Host Pending Deallocate' state before eventually deallocating the host. For additional assistance please reach out to Azure support.
 
 ### Q:  What will happen to my VMs if a Host is automatically deallocated?
 

articles/virtual-machines/dedicated-hosts-how-to.md

@@ -178,6 +178,7 @@ If you set a fault domain count for your host group, you'll need to specify the
 1. Select *myDedicatedHostsRG* as the **Resource group**.
 1. In **Instance details**, type *myHost* for the **Name** and select *East US* for the location.
 1. In **Hardware profile**, select *Standard Es3 family - Type 1* for the **Size family**, select *myHostGroup* for the **Host group** and then select *1* for the **Fault domain**. Leave the defaults for the rest of the fields.
+1. Leave the **Automatically replace host on failure** setting *Enabled* to automatically service heal the host in case of any host level failure.
 1. When you're done, select **Review + create** and wait for validation.
 1. Once you see the **Validation passed** message, select **Create** to create the host.
 
@@ -191,6 +192,7 @@ az vm host create \
    --name myHost \
    --sku DSv3-Type1 \
    --platform-fault-domain 1 \
+   --auto-replace true \
    -g myDHResourceGroup
 ```
 
@@ -205,7 +207,7 @@ $dHost = New-AzHost `
    -Location $location -Name myHost `
    -ResourceGroupName $rgName `
    -Sku DSv3-Type1 `
-   -AutoReplaceOnFailure 1 `
+   -AutoReplaceOnFailure True `
    -PlatformFaultDomain 1
 ```
 

articles/virtual-machines/dedicated-hosts.md

@@ -88,6 +88,27 @@ Known issues and limitations when using automatic VM placement:
 - You won't be able to redeploy your VM.
 - You won't be able to use DCv2, Lsv2, NVasv4, NVsv3, Msv2, or M-series VMs with dedicated hosts.
 
+## Host Service Healing
+
+In case of any failure relating to the underlying node, network connectivity or software issues can push the host and VMs on the host to a non-healthy state causing disruption and downtime to your workloads. The default action is for Azure to automatically service heal the impacted host to a healthy node and move all VMs to the healthy host. Once the VMs are service healed and restarted the impacted host will be deallocated. During the service healing process the host and VMs would become unavailable incurring a slight downtime. 
+
+The newly created host would have all the same constraints as the old host: 
+ - Resource group
+ - Region
+ - Fault Domain 
+ - Host Group
+ - ADH SKU  
+ - Auto replace on failure setting
+
+Users with compliance requirements might need a strong affinity between the host and underlying node and would not like to be automatically service healed, in such scenarios users can choose to opt out of auto service healing at host level by disabling the 'Automatically replace host on failure setting'.
+
+### Implications
+
+If you decide to disable auto service healing and if the underlying node encounters a failure your host state will change to 'Host Pending Deallocate' and will eventually be deallocated. 
+
+To avoid deallocation, you would need to manually redeploy the host by creating a new dedicated host and moving all the VMs from  the old host to the new host.
+
+The auto replace host setting is a create time setting and cannot be changed once the host is created. VMs that are manually stopped/deallocated from the impacted host are not moved as part of the automatic service healing.
 
 ## Virtual Machine Scale Set support