By Crystal / Last Updated June 16, 2022

Why merge VMDK files into a single one?

When you create a VM, there’s a step that lets you specify the disk capacity. Due to the limitation of FAT32, you may split virtual disk into multiple files to make each file smaller than 4 GB, and it will also be easier to move or copy the split VMDK in VMware.

disk space

However, multiple VMDK files may lead to poor performance of VM once they occupy large space of disk. To improve performance, you may want to merge multiple VMDK files into one disk.

In this article, I will explain how to merge VMDK files into one file in VMware Workstation, VMware Fusion or VMware Player, and introduce how to protect VMDK files efficiently.

How to merge VMDK files into a single file

If you want to merge several VMDK files into a single VMDK file, you need to install Virtual Disk Manager (vmware-vdiskmanager) first. It is a utility that you can use it to create, manage, and modify virtual disk files from the command line.

You can use Virtual Disk Manager with virtual disks created under VMware Workstation 5 or higher, VMware Fusion, VMware Player, VMware ESX/ESXi server, etc.

Some of these platforms come with this file, while some do not have it. If you are using VMware Workstation or VMware Fusion, you can find it easily in your virtual machine software folder, but if you are using VMware Player, you can install this utility first in VMware website.

After ensuring you installed the vdiskmanager.exe, the remain steps are roughly the same. As examples, I will explain how to merge multiple VMDK files into one in some different situations.

vmware

Merge multiple VMDK files in VMware Workstation/Fusion

If you are using VMware Workstation or VMware Fusion, it is easy to access VMware-vdiskmanager and use it to merge source disks into a new single disk. Before you merge VMDK files, you should backup the virtual machine first.

Tips: Besides, if you want to open VMDK files on VMware Workstation, you can mount a VMDK file to a virtual machine.

How to merge VMDK files into a single file:

1. Shut down the VM, and find the location of split VMDK files.

2. Find the VMware Workstation file and locate the vmware-vdiskmanager.exe on this folder, then do the following steps:

☛ Copy the path: C:\Program Files (x86)\VMware\VMware Workstation\vmware-vdiskmanager.exe

☛ Copy the source disk of VM: G:\Windows 10 x64.vmdk (original source file)

☛ Create a new destination folder for the new single file: G:\newimage\newimage.vmdk (destination file)

3. Open command prompt, then enter the command, for example:

"C:\Program Files (x86)\VMware\VMware Workstation\vmware-vdiskmanager.exe" -r "G:\Windows 10 x64.vmdk" -t 0 "G:\newimage\newimage.vmdk"

converting multiple files

4. You can check the status, and the new single VMDK file will be created in the destination folder when it finishes to convert the multiple VMDK files.

a single vmdk file

5. After the new VMDK file is created, please move the original files into other directory, and rename the new VMDK file as the original one “Windows 10 x64.vmdk”

Now you finish the process to merge multiple VMDKs into a single file in Workstation. Please choose to use an existing virtual disk (using the new single VMDK file) to create a virtual machine.

use single vmdk file to create VM

Merge multiple VMDK files into one in VMware Player

If you are using VMware Player, you may find that VMware Player do not come with vdiskmanager. So, you should download it first in VMware website and refer to the following steps to combine VMDK files into one.

How to merge multiple VMDKs step by step:

1. Click here to start download vdiskmanager.

2. Unzip and rename 1023856-vdiskmanager-windows-7.0.1.exe into vmware-vdiskmanager.exe.

install vdiskmanager

3. Copy or move to the directory where VMware Player is installed.

⊹ If you see the denied notice while copying, click Continue.

⊹ After successful copy, right click the vdiskmanager >> Properties >> Unblock >> Apply.

vdiskmanager properties

4. Now, open the command prompt and enter this command as before:

☛"C:\Program Files (x86)\VMware\VMware Player\vmware-vdiskmanager.exe" -r  “C:\temp\Win2012R2\Windows Server 2012.mdk” -t 0 “C:\temp\Win2012R2_New\Win2012R2_New.vmdk”

converting vmdk files in vmware player

5. Then you will get a combined single VMDK file in VMware Player.

Some users may be confused about command line and worry about human errors to cause data loss when merging VMDK files, and some users find that the virtual disk is not bootable after merging. It's necessary to backup your virtual disk first before merging multiple VMDK files.

Important: Backup VMDK files securely before merge

Backup is critical before making big changes. Here, I will use  a professional backup software to protect virtual disk.

AOMEI Centralized Backupper provides you a simple interface to backup virtual disks with several clicks. Furthermore, as a centralized backup solution, it centralized the features of File, System, Disk, Partition, and SQL Server Backup, as well as Basic Sync, Real-Time Sync, and Mirror Sync.

Please download and install AOMEI Centralized Backupper on your computer. Here’s a 30-day free trial:

Download Free TrialVMware ESXi & Hyper-V
Secure Download

1. Install Agent on all the client computers you want to backup. You can launch Centralized Backupper, switch to Computers tab, and choose to Install client program manually or remotely.

*The client programs installed remotely will be auto controlled by the central machine, but if you choose the manual way, you still need to Request Control over them.

install client program

Then go to Tasks tab and create a New Task as you need. The options include file, system, partition, disk and SQL Server. Here, choose Disk Backup to get started.

disk backup

2. The backup setup screen is divided into three steps. In Step 1, you can click + Add Computers to detect all the controlled computers, and select the ones you want to backup.

select computers

3. In Step 2, you can either Select data based on a client (manual selection), or Select data based on backup rules (auto selection). 

disk backup based on backup rules

4. Click on Step 4, and click Add Storage to enter the network path of a share or NAS, then specify a folder in it as the target directory. 

add storage

5. After the basic setup, you can manage Settings, or create a ScheduleScheme to customize the backup, then click Start Backup to create and execute the task.

start backup

Setting: Manage compression level, image spitting, backup mode (intelligent sector or exact backup), notifications, etc.

backup settings

Schedule: Set up automatic backup Once/Daily/Weekly/Monthly, and choose to perform Full Backup/Incremental Backup/Differential Backup.

schedule backup

Scheme: Create a rule to auto delete backup older than x days and therefore save your storage space.

backup scheme

6. The created backup tasks will be listed under Tasks tab, then you can directly manage it here. 

manage backup tasks

Frequently Asked Questions about VMDK file

Q: What happens if I delete VMDK files?

A: If you delete them, you will lose your VM data and corrupt your VM. Unless you have no longer need them, please do not delete them.

Q: How to split one VMDK file into several VMDK files?        

A: The procedures are similar to the process of merging multiple VMDK files, pay attention to changing -t 0 into -t 1.

Shut down the VM >> open a command prompt in Windows >> C:\Program Files (x86)\VMware\VMware Workstation\vmware-vdiskmanager.exe -r sourceDisk.vmdk -t 1 destinationDisk.vmdk

Summary

If you want to optimize the performance of your VM, I recommend you to follow these steps to merge VMDK files into a single one, and do not forget to back up your important data before merging VMDK.