VMWare Replication: How to Increase Disk Space

What is VMWare Replication

VMWare Replication is an asynchronous replication solution that is capable of protecting Virtual Machines from a source location in a target location. The target can be another data center, or a cloud hosting provider.

It is a licensed product where you are charged for replication licenses per virtual machine. VMware usually sells them in blocks of 25 virtual machines at a time. You must also be running VMware vSphere Standard or Enterprise edition, it will not work on Essentials or Essentials Plus licenses.

VMWare Replication has been known by various product names throughout its lifetime, it is commonly known as Site Recovery Manager (SRM), vSphere Replication or vSphere Data Protection (VPD).

Throughout this article, I will refer to it as SRM.

Why is it so hard to increase disk space in SRM?

One of the most common issues introduced by VMWare Replication software is the inability to expand disk space on a server.

If you attempt to increase disk space on a source virtual machine, that change will not automatically be transferred to the disaster recovery replica. If a sysadmin does expand the disk space, it will break replication and potentially take the VM offline.

Increasing hard disk capacity is one of the most common tasks system administrators have to do. These days to extend hard disk space, the operating system does all the hard work for you, Windows Disk Manager can extend any disk (including the system disk) without even rebooting the server. It’s the same for Linux, but VMware is a different story and it’s one of the challenges introduced with vSphere replication.

This common task is still possible to do, but you must approach it slightly differently.

Infrastructure Overview:

In this demo I will be running VMware vSphere 6.5 Enterprise Plus license, the infrastructure consists of:

• Locations:
  • Two physically separate sites, geographically distant from each other.
• Network Connectivity:
  • Primary Connection: 10GB production “dark fiber” network.
  • Backup Connection: 4GB link.
• Server Configuration (Per Location):
  • Hosts: 8 ESXi hosts.
  • Storage: Dedicated IBM XIV object storage.
  • Networking: 40GB Infiniband.

Step 1: Accessing the VMware Infrastructure

Access Primary Site:

• Open the VMware Web Client.
• Log onto the vCenter at the Primary Site.

Access Recovery Site:

• Using the VMware Web Client, log onto the vCenter at the Recovery Site.

Navigate to vReplication:

• On the vCenter (Primary Site), go to the home page.
• Select Monitor and then choose vSphere vReplication.

Step 2 – Information gathering at the source location

Access Outgoing Replications:

• Navigate to Outgoing Replications.

Identify the Server:

• Find the server for which you want to expand the disk space. For this guide, we’ll use TEST2016T as an example.

Configure vReplicator:

• Highlight the chosen server.
• Click on the Configure vReplicator button.

Authentication:

• When prompted, log in using your vCenter account credentials.

Locate Datastore Information:

• Click on Target Location and expand the details by pressing the arrow.
• Take note of the Datastore name. This indicates where the replicated disk data resides. Remember, the name you see might differ from our example.

Exit Configuration:

• After noting the necessary details, exit by clicking CANCEL on the configuration wizard.

Step 3: Gathering Information from the Target Location

Switch to Recovery Site:

• Transition to the vCenter at the Recovery Site.

Rename VM Folder:

• Rename the folder where the virtual machine’s replicated data is stored. This step ensures that the replicated data remains intact when replication from the virtual machine is removed.

Navigate to Datastore:

• Go to Datastore and then to the specific Folder Name where the replicated data is stored.

Example

Step 4: Terminating the Current Replication

Return to Primary Site:

• Navigate back to the vCenter at the Primary Site.

Deactivate Replication:

• Identify the virtual machine you wish to resize.

• Select the server, right-click on it, and choose Stop to disable its replication.

• Click ok to the warning message

Step 5 – Expand the servers disk space in vCenter

Access vCenter at Primary Site:

• Navigate to the vCenter at the Primary Site.

Modify Virtual Machine Disk Size:

• Locate and select your desired server.
• Right-click on the server and choose Edit Settings.
• In the settings menu, input the new desired disk size for the volume.

Step 6 – Expand the Volume on an ESXi Host

Access vCenter at Secondary Site:

• Navigate to the vCenter at the Secondary Site.

Enable SSH:

• Activate the SSH service within vCenter.

SSH into a Server:

• Using a terminal application, such as Putty, establish an SSH connection to any server at the secondary location. Ensure that the chosen ESXi host has the storage LUN already mapped.

Locate the Server on the Datastore:

• Once connected, navigate to the datastore volume and identify the server name.

Change Directory to Target Location:

• Use the following command to switch to the datastore and specific folder where the replicated disk resides:

For example:

cd /vmfs/volumes/ITO2-7001N-DS03/TEST2016T-OLD

Substitute TEST2016T-OLD for your server

Use vmkfstools:

• Once you’re in the correct directory where the replicated disk is stored, utilize the vmkfstools command to resize the VMDK. Ensure you’re aware of the disk number you modified in vCenter.

vmkfstools -X [new size]G [server_name]-disk[number].vmdk

Replace:

• [new size] with the desired disk size.
• [server_name] with the name of your server.
• [number] with the specific disk number you’ve changed in vCenter.

Note:

• It’s crucial to have a backup of your data and to be certain about the disk number and size before executing the command to prevent any data loss or misconfiguration.

For Example:

vmkfstools -X 102GB TEST2016T.vmdk

Substitute TEST2016T.vmdk for your server

Note: The preceding command increases the size of a virtual disk to 102 GB. Substitute this for YOUR VALUE

Step 7 – Re-enable Replication

• At the recovery site vCenter (Recovery Site), Rename the virtual machine folder to the original name.

• At vCenter (Primary Site) – Reconfigure the replication for the virtual machine. Ensure to select the Specify datastore folder option to select the folder in which the replicated disk is stored.

• Click on the Server name > Actions > All vSphere Replication Actions > Configure vReplication

• Choose Replicate to a vCenter Server

• Choose Recovery Site Appliance as Replicated site

• Choose a vReplicator appliance

IMPORTANT – On Target location point the server storage to the original location of the replicated data.

In this example it was ITO2-7001N-DS03 – Yours will be different.

Ensure you choose the correct folder too.

IMPORTANT – Chose USE EXISTING when you get the following warning

IMPORTANT – Change the USING SEED option to YES by clicking USE ALL SEEDS

This will use the existing data ensuring that the entire server does not need to be replicated from scratch, useful if you have large servers.

BEFORE

AFTER

• Ensure Guest OS quiescing and Network compression are unticked

• Leave RPO at pre-define timings. In my example this is set to 4 hours

Step 8 – Monitor until completion

• Now Next, Next finish to complete the process
• Monitor the status in the Recent Task section of vCenter
• Disable SSH service on host

Step 9 – Check the Operating System to make sure the disk has expanded

• In Windows, you will need to check Windows Disk Management and expand the disk in the GUI
• In Linux, you will need to manually expand the filesystem, the process of this varies depending on what format the disk is written in+