Configuring Disaster Recovery with Metro

Objective

This guide introduces Metro Availability, which provides an automated disaster recovery plan.

Requirements

• Access to the OVHcloud Control Panel
• Access to your clusters via Prism Central
• You need to have 3 Nutanix clusters within the OVHcloud infrastructure with Pro or Ultimate packs if you have a Nutanix on OVHcloud packaged service on both clusters in the P.R.A. These 3 clusters will need to be at remote sites for maximum security.
• You must have less than 5 ms of latency between the two replicated clusters. Please note that latency is not covered by SLAs.

Introduction s

We will set up a two-way disaster recovery plan between two clusters with this hardware:

• A Nutanix cluster in Roubaix, France, with virtual machines replicated in Gravelines.
• A Nutanix cluster in Gravelines, France, with virtual machines replicated in Roubaix.
• A Nutanix cluster in Erith, England with Prism Central to serve as a witness in the disaster recovery plan.

We will only use one vRack, which will contain:

• The three Nutanix clusters.
• Load balancers.
• Additional IP addresses on the rtvRack.

Below is the diagram showing the three sites:

Instructions

• Step 1 Configuration
  • Step 1.1 Interconnection of the three clusters
  • Step 1.2 Delete the Prism Central records for the Roubaix and Gravelines clusters
  • Step 1.3 Register both clusters on Prism Central in Erith
  • Step 1.4 Adding IP Addresses for iSCSI Connections on All Three Clusters
  • Step 1.5 Creating two Storage Containers
  • Step 1.6 Move virtual machines to the Storage Container
  • Step 1.7 Creation of a category to be used when implementing the P.R.A.
  • Step 1.8 Add virtual machines in categories
  • Step 1.9 Setting up synchronous replications between Roubaix and Gravelines
  • Step 1.10 Create Subnets for Disaster Recovery Plan
  • Step 1.11 Implementation of disaster recovery plans
• Step 2 - Validate Disaster Recovery Plan
  • Step 2.1 Monitoring the Disaster Recovery Plan
  • Step 2.2 Live migration of virtual machines from Roubaix to Gravelines
  • Step 2.3 Operations after a migration
  • Step 2.4 Execute the Disaster Recovery Plan in Real Condition

We will implement this disaster recovery plan step by step.

The cluster configuration information used in our guide is as follows:

• Roubaix cluster:

  • Server 1: VM address CVM 192.168.0.21, hypervisor IP address AHV 192.168.0.1.
  • Server 2: VM address CVM 192.168.0.22, hypervisor IP address AHV 192.168.0.2.
  • Server 3: VM address CVM 192.168.0.23, hypervisor IP address AHV 192.168.0.3.
  • Prism Element virtual address: 192.168.0.100.
  • Prism Element iSCSI address: 192.168.0.102.
  • Prism Central IP address: 192.168.0.101.
  • Gateway: 192.168.3.254.
  • Mask: 255.255.252.0
  • Cluster version: 6.5

• Gravelines cluster:

  • Server 1: VM address CVM 192.168.1.21, hypervisor IP address AHV 192.168.1.1.
  • Server 2: VM address CVM 192.168.1.22, hypervisor IP address AHV 192.168.1.2.
  • Server 3: VM address CVM 192.168.1.23, hypervisor IP address AHV 192.168.1.3.
  • Prism Element virtual address: 192.168.1.100.
  • Prism Element iSCSI address: 192.168.1.102.
  • Prism Central IP address: 192.168.1.101.
  • Gateway: 192.168.3.254.
  • Mask: 255.255.252.0
  • Cluster version: 6.5.

• Erith Cluster:

  • Server 1: VM address CVM 192.168.2.21, hypervisor IP address AHV 192.168.2.1.
  • Server 2: VM address CVM 192.168.2.22, hypervisor IP address AHV 192.168.2.2.
  • Server 3: VM address CVM 192.168.2.23, hypervisor IP address AHV 192.168.2.3.
  • Prism Element virtual address: 192.168.2.101.
  • Prism Element iSCSI address: 192.168.2.102.
  • Prism Central IP address: 192.168.2.100.
  • Gateway: 192.168.3.254.
  • Mask: 255.255.252.0
  • Cluster version: 6.5.

In addition to this guide, you can use these documents:

• Nutanix hyperconvergence
• advanced tools

Step 1 - Configuration

Step 1.1 - Interconnection of the three clusters

The first step is to interconnect the three clusters on the same OVHcloud vRack.

Use this guide to connect your clusters: Interconnect clusters through the vRack. To connect the three clusters, use the instructions provided in the guide:

• Roubaix clusters in the vRack dedicated to Gravelines.
• Erith clusters in the vRack dedicated to Gravelines.

When you have finished configuring your vRack, you will have these elements in your vRack:

• 9 dedicated servers (3 per cluster)
• 3 public IP addresses
• 3 Load Balancers

The three clusters are currently accessible from the Prism Central URL of each cluster.

Step 1.2 - Delete the Prism Central records for the Roubaix and Gravelines clusters

To implement a disaster recovery plan solution with Metro Availability, a cluster witness is required to automate tasks in the event of one of the clusters becoming unavailable. The cluster witness is located on a Prism Central virtual machine.

The Erith cluster will host the Prism Central virtual machine for the three clusters, and serve as a cluster witness for the disaster recovery plan between Roubaix and Gravelines.

Disabling Prism Central on the Roubaix cluster

Connect via SSH to the Prism Element cluster in Roubaix:

ssh nutanix@private_ip_address_prism_element_Roubaix
Enter Prism Element password

Run this command to remove Prism Element from the Prism Central configuration:

ncli multicluster remove-from-multicluster external-ip-address-or-svm-ips=private_ip_address_central_roubaix\
username=admin password=pwd_pe_Roubaix force=true

This message appears when disconnecting from Prism Central.

Cluster unregistration is currently in progress. This operation may take a while.

Enter this command:

ncli cluster info

Note the value of the Cluster UUID that must have this form xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

Disconnect from Prism Element and connect via SSH on the Prism Central virtual machine in Roubaix.

ssh nutanix@private_ip_address_prism_central_roubaix
Enter Prism Central password

Enter this command:

python /home/nutanix/bin/unregistration_cleanup.py cluster_uuid_prism_element_Roubaix

Disabling Prism Central on the Gravelines cluster

Log in to the Prism Element cluster in Gravelines via SSH.

ssh nutanix@private_ip_address_prism_element_Gravelines
Enter Prism Element password

Enter this command:

ncli multicluster remove-from-multicluster external-ip-address-or-svm-ips=private_ip_address_prism_central_Gravelines\
username=admin password=pwd_pe_Gravelines force=true

This message appears when disconnecting from Prism Central.

Cluster unregistration is currently in progress. This operation may take a while.

Enter this command:

ncli cluster info

Note the value of Cluster UID that should be in this form xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

Disconnect from Prism Element and connect via SSH on the Prism Central virtual machine in Gravelines.

ssh nutanix@private_ip_address_prism_central_Gravelines
enter Prism Central password
python /home/nutanix/bin/unregistration_cleanup.py cluster_uuid_prism_element_Gravelines

Step 1.3 - Registration of the two clusters on the Prism Central in Erith

Log in to the Prism Element in Roubaix via SSH:

ssh nutanix@private_ip_address_prism_element_Roubaix
enter Prism Element password

Run this command:

ncli multicluster register-to-prism-central username=admin password=passwod_admin\ external-ip-address-or-svm-ips=private_ip_address_prism_central_Erith

This message appears:

Cluster registration is currently in progress. This operation may take a while.

Wait and enter this command:

ncli multicluster get-cluster-state

If the cluster is connected to Prism Central in Erith, you will see this information:

Registered Cluster Count: 1

    Cluster Id                : xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
    Cluster Name              : Prism-Central-Erith-FQDN
    Is Multicluster           : true
    Controller VM IP Addre... : [private_ip_address_prism_central_Erith]
    External or Masqueradi... :
    Cluster FQDN              :
    Controller VM NAT IP A... :
    Marked for Removal        : false
    Remote Connection Exists  : true

Log in to Prism Element in Gravelines via SSH:

ssh nutanix@adresse_ip_prism_element_Gravelines
Enter Prism Element password from Gravelines

Run this command:

ncli multicluster register-to-prism-central username=admin password=passwod_admin_Erith external-ip-address-or-svm-ips=private_ip_address_central_Erith

This message appears:

Cluster registration is currently in progress. This operation may take a while.

Wait and enter this command:

ncli multicluster get-cluster-state

If the cluster is connected to the Prism Central in Erith, you will see this information:

Registered Cluster Count: 1

    Cluster Id                : xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
    Cluster Name              : Prism-Central-Erith-FQDN
    Is Multicluster           : true
    Controller VM IP Addre... : [private_ip_address_prism_central_Erith]
    External or Masqueradi... :
    Cluster FQDN              :
    Controller VM NAT IP A... :
    Marked for Removal        : false
    Remote Connection Exists  : true

From a web browser, log in to the URL from Prism-Central to Erith, you will see the three clusters.

The Prism Central virtual machines in Gravelines and Roubaix are no longer being used. You can stop them.

In the main menu, click Vms in the Compute & Storage submenu.

Select the Prism Central virtual machines in Gravelines and Roubaix and click Guest Shutdown from the Actions menu.

Step 1.4 - Adding IP Addresses for iSCSI Connections on All Three Clusters

From the Prism Central dashboard, click the link to the Erith cluster .

On the Prism Element dashboard, click the cluster name in the top left-hand corner.

Scroll down the window and check the IP address in ISCSI Data Services IP.

From the Prism Central dashboard, click the link to the "Gravelines cluster".

On the Prism Element dashboard, click "the cluster name" in the top left-hand corner.

Scroll down the window and check the IP address in ISCSI Data Services IP.

From the Prism Central dashboard, click on the link to the "Roubaix cluster".

On the Prism Element dashboard, click the "cluster name" in the top left-hand corner.

Scroll down the window and check the IP address in ISCSI Data Services IP.

Step 1.5 - Creating Two Storage Containers

We will create two Storage Containers with the same name, one in Roubaix and the other in Gravelines.

From the Prism Element main menu, click Storage Containers in the Compute & Storage submenu.

Click Create Storage Container.

Type UsedForDR in Name, choose the Roubaix cluster in Cluster, and click Create.

Click Create Storage Container.

Type UsedForDR in Name, choose the Gravelines cluster in Cluster, and click Create.

In the list of Storage Containers, you will see two Storage Containers with the same name. One on the Roubaix cluster and the other on the Gravelines cluster.

Step 1.6 - Moving virtual machines to the Storage Container

We will move the virtual machine storage to the Storage Container we have created.

Connect via SSH on the Prism Element of the Roubaix cluster:

ssh nutanix@private_ip_address_Prism_element_Roubaix
Enter the Nutanix account password of Prism Element

Run this command for each VM we will move to the Storage Container, replacing vmname with the name of the virtual machine (in our disaster recovery plan, we have two virtual machines in Roubaix, one on Windows and one on Linux).

acli vm.update_container vmname container=UsedForDR
Enter the Nutanix account password of Prism Element

Log in to the Prism Element of the Gravelines cluster via SSH:

ssh nutanix@private_ip_address_Prism_element_Gravelines
Enter the Nutanix account password of Prism Element

Execute this command for each VM that we will move to the Storage Container, replacing vmname with the name of the virtual machine (in our disaster recovery plan, we have three virtual machines in Gravelines, one on Windows, another on Linux and the gateway that gives access to the Internet).

acli vm.update_container vmname container=UsedForDR
Enter the Nutanix account password of Prism Element

Step 1.7 - Creation of a category to be used when implementing the P.R.A

We will create a category with two values in Prism Central to assign the virtual machines involved in replication.

Scroll through the main menu, click Categories on the Administration submenu.

Click New Category.

Type Protected VM in Name, add the Roubaix and Gravelines values in Values and click on the next button Save.

The category appears in the list and is ready to use.

Step 1.8 - Adding virtual machines in categories

We will assign two virtual machines on the Roubaix cluster in one category and three virtual machines on the Gravelines cluster in another category.

From the Prism Central main menu, click Vms in the Compute & Storage submenu.

Select the two virtual machines in Roubaix on the left, then on the Actions menu, click Manage Categories.

Add the category ProtectedVM: Roubaix, then click Save.

Select the three virtual machines in Gravelines on the left, and on the Actions menu, click Manage Categories.

Add the category ProtectedVM: Gravelines, then click Save.

Step 1.9 - Setting up synchronous replications between Roubaix and Gravelines

Synchronous replication allows permanent replication with 0 seconds of data loss.

Replication setup between Roubaix and Gravelines

On the Prism Central main menu, click Protection Policies in the Data Protection submenu.

Click Create Protection Policy.

Type ROUBAIX-TO-GRAVELINES in Policy name, keep Local AZ, and click Select Cluster in Primary Location.

Choose the Roubaix cluster and click Save.

In the top left-hand corner next to Disaster Recovery, click Enable.

The system checks that everything is correct before enabling Disaster Recovery.

Click Enable to enable the Disaster Recovery option.

Click Enable again.

Your Disaster Recovery option is being activated.

Keep Local AZ, select the cluster in Recovery Location and click Save.

Click + Add Schedule.

Choose Synchronous for Protection Type and Automatic for Failure Detection Mode. Then click Save Schedule.

Click Next.

Select the category ProtectedVM : Roubaix and click Add.

Click Create.

Virtual machines in Roubaix are now replicated to Gravelines. You must wait for a first full replication to have permanent replication.

Replication setup between Gravelines and Roubaix

Replication can be two-way. We will now create replication from Gravelines to Roubaix.

Click Create Protection Policy.

Choose as name GRAVELINES-TO-ROUBAIX in Policy Name, keep Local AZ and choose Gravelines cluster in Primary Location. Then click Save.

Keep Local AZ, select the Roubaix cluster and click Save.

Click + Add Schedule.

Choose Synchronous for Protection Type and Automatic for Failure Detection Mode. Then click Save Schedule.

Click Next.

Select the category ProtectedVM: Gravelines and click Add.

Click Create.

A second protection strategy is in place.

Step 1.10 - Create Subnets for Disaster Recovery Plan

We will create subnets that will be used to test disaster recovery plans.

For each existing subnet, a test network is required. On the two clusters of the Disaster Recovery Plan, we have three production subnets.

• based on VLAN 0.
• infrastructure on VLAN 1.
• production on VLAN 2.

We will therefore create 3 additional subnets on the Gravelines and Roubaix clusters with these names:

• testing on VLAN 100.
• testinfra on VLAN 101.
• production on VLAN 102.

Use this guide to create VLANs on your Nutanix clusters: isolate production management machines.

In the Prism Central Subnets dashboard, you will see six new subnets.

Step 1.11 - Implementation of disaster recovery plans

Now that the replications and subnets are in place, we will implement automated or manual disaster recovery plans on demand to:

• migrate virtual machines on the fly between the two clusters
• Test that replication is working properly
• Automatically restart the VMs that are members of the P.R.A in the event of a failure of one of two clusters.

Creation of a disaster recovery plan for the Roubaix cluster

In the main menu of Prism Central, click Recovery Plans in the Data Protection submenu.

Click on Enable Disaster Recovery on the left.

Normally, the recovery plan must be activated as indicated with the message Disaster Recovery enabled. Click on the right to close this window.

Click Create New Recovery Plan.

Choose this information:

• Recovery Plan Name: Recovery VM from ROUBAIX to GRAVELINES.

• Primary Location: Local AZ.

• Primary Cluster: cluster in Roubaix.

• Recovery Location: Local AZ.

• Recovery Cluster: cluster in Gravelines.

• Failure Execution Mode: Automatic.

• Execute failover after disconnectivity of: 30 seconds.

Then click Next.

Click + Add VM(s).

Select both virtual machines and click Add.

Click Next.

Click OK. Got it.

Click Stretch networks.

Click Proceed.

Choose the VLANs that will be used during the IP like this:

• Primary
  • Production : production
  • Test Failback : testproduction
• Recovery
  • Production : production
  • Test Failback : testproduction

Then click Done.

Creation of a disaster recovery plan for the Roubaix cluster

The Disaster Recovery Plan has been created for the Roubaix site. Click Create Recovery Plan to create the Gravelines Disaster Recovery Plan.

Choose this information:

• Recovery Plan Name: Recovery VM from Gravelines to Roubaix.

• Primary Location: Local AZ.

• Primary Cluster: cluster in Gravelines.

• Recovery Location: Local AZ.

• Recovery Cluster: cluster in Roubaix.

• Failure Execution Mode: Automatic.

• Execute failover after disconnectivity of: 30 seconds.

Then click Next.

Click + Add VM(s).

Select the three virtual machines and click Add.

Click Next.

Click Stretch networks.

Click Proceed.

Choose this information:

• Primary
  • Production: basis
  • Failback test: test
• Recovery
  • Production: basis
  • Failback test: test

Then click + Add Network Mapping.

Choose this information:

• Primary
  • Production : infra
  • Test Failback : testinfra
• Recovery
  • Production : infra
  • Test Failback : testinfra

Then click + Add Network Mapping.

Choose this information:

• Primary
  • Production : production
  • Test Failback : testproduction
• Recovery
  • Production : production
  • Test Failback : testproduction

Then click Done.

Both disaster recovery plans are in production.

Step 2 - Validate Disaster Recovery Plan

Step 2.1 - Monitoring the Disaster Recovery Plan

Using the Commit to Disaster Recovery Plan Option

You can validate the disaster recovery plan via Prism Central.

Click on the Recovery VM from Roubaix to validate and test.

Click Validate

Select the Roubaix cluster for Entity Failing Over From and the Gravelines cluster for Entity Failing Over To. Then click Proceed

The recovery plan has been validated. Click Close

Test Disaster Recovery Plan

We can test the disaster recovery plan without impacting production. The test creates virtual machines with different names on the destination cluster in the VLANs created earlier.

Click Test.

Select the Roubaix cluster for Entity Failing Over From and the Gravelines cluster for Entity Failing Over To. Then click Test.

Click Execute Anyway.

Go to the VM dashboard in Prism Central and you will see the test virtual machines that are created with the replicated data.

Return to your recovery plan and click Clean-up test entities to remove the test virtual machines.

Click Clean Up

Step 2.2 - Live migration of Roubaix virtual machines in Gravelines

On a fully operational infrastructure, it is possible to move virtual machines from one cluster to another without any service downtime.

Go to a virtual machine in Roubaix that is part of the recovery plan. We will ping the OVHcloud DNS server 213.186.33.99.

Return to your recovery plan and click Failover on the More menu.

Choisissez Planned Failover, cochez Live Migrate Entities.

Take the Roubaix cluster for Entity Failing Over From and the Gravelines cluster for Entity Failing Over To.

Then click Failover.

Type Failover and click Failover.

Hot migration is in progress.

The migration was completed successfully without any service downtime.

You can go back to the virtual machine and see that the ping continues to work even if the virtual machine has been moved from one cluster to another.

Step 2.3 - Operations after a hot migration

After a migration, it is necessary to reverse the replication and operation of the disaster recovery plan.

Reverse Replication

On the Prism Central main menu, click Protections Policies in the Data Protection submenu.

Click on the protection plan named ROUBAIX TO GRAVELINES.

Click Update.

Position the mouse below the Roubaix cluster name in Primary Location and click Edit.

Check the Gravelines cluster instead of the Roubaix cluster.

Click Save.

Click Update Location.

Position the mouse below the Gravelines cluster name in Recovery Location and click Edit.

Select the Roubaix cluster instead of the Gravelines cluster.

Click Save.

Click Update Location.

Click Next.

Click Update.

Replication is reversed, click the button to close the protection plan.

Disaster Recovery Plan Reverse

In the main menu of Prism Central, click Recovery Plans in the Data Protection submenu.

Click Recovery VM from Roubaix to Gravelines.

On the More menu, click Update.

In locations, put the Gravelines cluster in Primary CLusters and the Roubaix cluster in Recovery Clusters and then click Next.

Click Proceed.

Click Next.

Choose this information:

• Primary
  • Production : production
  • Test Failback : testproduction
• Recovery
  • Production : production
  • Test Failback : testproduction

Click Done.

Step 2.4 - Execute the Disaster Recovery Plan in Real Condition

We will simulate a total loss of connection to Gravelines where three virtual machines are located in the disaster recovery plan (the Internet gateway and two other virtual machines).

Log in to the command line and ping the public address of the gateway.

## Ping from a remote linux console
ping xx.xx.xx.xx
Reply from xx.xx.xx.xx: bytes=32 time=21ms TTL=58
Reply from xx.xx.xx.xx: bytes=32 time=21ms TTL=58
Reply from xx.xx.xx.xx: bytes=32 time=23ms TTL=58
Reply from xx.xx.xx.xx: bytes=32 time=20ms TTL=58

Leave the ping command to run continuously and return to Prism Central.

In the main menu, click VMs in the Compute & Storage submenu.

The three virtual machines in the disaster recovery plan are functional.

All three nodes in the Gravelines cluster will be disconnected.

Return to the console that is pinging to the gateway, and you will see a connection loss.

Reply from xx.xx.xx.xx: bytes=32 time=20ms TTL=58
Reply from xx.xx.xx.xx: bytes=32 time=21ms TTL=58
Reply from xx.xx.xx.xx: bytes=32 time=20ms TTL=58
Reply from xx.xx.xx.xx: bytes=32 time=20ms TTL=58
Reply from xx.xx.xx.xx: bytes=32 time=20ms TTL=58
Request timed out.
Request timed out.
Request timed out.
Request timed out.

In Prism Central, click the top right on the tasks to display the task launch, including Recovery plan execute.

Go back to the text console and you will see that the ping works again.

Request timed out.
Reply from xx.xx.xx.xx: bytes=32 time=20ms TTL=58
Reply from xx.xx.xx.xx: bytes=32 time=19ms TTL=58
Reply from xx.xx.xx.xx: bytes=32 time=18ms TTL=58
Reply from xx.xx.xx.xx: bytes=32 time=18ms TTL=58
Reply from xx.xx.xx.xx: bytes=32 time=19ms TTL=58
Reply from xx.xx.xx.xx: bytes=32 time=19ms TTL=58

Go to Prism Central in the virtual machine management, you will see the three virtual machines of the recovery plan in duplicate. They are marked as started, but in reality, only the ones restarted in Roubaix are working.

We will reconnect the three nodes in the vRack to return to normal mode.

After the recovery, the virtual machines on the original cluster are still visible but are turned off. You can delete or keep them if problems occur on the VMs that are being rebooted.

You can view the history of Disaster Recovery actions in Prism Central.

Click the button in the top right-hand corner to go to the Prism Central configuration.

Left-click Witness and click View Usage History.

The list of events appears, click Close to close.

Go further

Interconnect clusters through the vRack

Disaster Recovery Plan for Nutanix

Asynchronous or NearSync replication through Prism Element

Advanced replication with Leap

Introduction to vRacks

Documentation Nutanix AHV Metro - Witness Option

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