Creating a virtual hard drive can provide additional storage, improve performance, or allow you to run multiple operating systems on one physical computer. Virtual hard drives are file containers that behave like physical disks but have the benefits of being software-based. There are a few different ways to create a virtual hard drive depending on your needs.
What is a Virtual Hard Drive?
A virtual hard drive is a file that emulates a physical hard drive. This allows you to treat the file as if it were a separate disk drive even though it does not exist physically. Virtual hard drives provide a layer of abstraction between the software and hardware, enabling portability and flexibility.
Some key advantages of using a virtual hard drive include:
- Adding more storage capacity without adding physical disks
- Isolating environments, applications, or operating systems
- Improving performance by allowing better distribution of I/O
- Portability – virtual drives can be easily moved between systems
Virtual hard drives can be created using disk image files or through disk management tools like Disk Management on Windows or Disk Utility on Mac. The process involves allocating disk space, formatting, and mounting the virtual drive for use by the operating system.
Creating a Virtual Hard Drive Using Disk Images
One way to create a virtual hard drive is from a disk image file. A disk image is a single file that contains the complete contents and structure of a hard drive or other type of media. Popular disk image formats include ISO, VHD, VMDK, and VDI files.
Here is how to create a virtual hard drive from a disk image file:
- Obtain a disk image file, either by creating your own or downloading one
- Ensure your virtualization software supports the disk image format you want to use
- Create a new virtual machine and configure the settings
- Add a new virtual hard drive and select the option to use an existing disk image file
- Specify the location of your disk image file
- Complete the virtual machine creation and power it on
This will connect the disk image to your new virtual machine, allowing you to access it like a physical disk drive. A key benefit of using disk images is portability since the image file can be easily copied to other systems.
Creating Disk Images
If you want to create your own custom disk image, tools like dd on Linux, PowerShell on Windows, and hdiutil on Mac provide options to generate image files from physical disks or folders.
For example, to create a VHDX disk image file on Windows:
PowerShell Convert-VHD -Path C:\DiskImage.vhdx -DestinationPath C:\SourcePhysicalDisk.vhdx -Confirm:$false
This will create a VHDX image file from an existing physical disk that can then be attached as a virtual drive.
Using Disk Management
On Windows, you can use the built-in Disk Management utility to create new virtual hard drives without needing a disk image.
Here is how to create a virtual hard drive with Disk Management on Windows:
- Open Disk Management (diskmgmt.msc)
- Select Action > Create VHD to launch the Create Virtual Hard Disk Wizard
- Choose your disk format (VHD or VHDX)
- Specify storage location and size for the new virtual disk
- Select Fixed or Dynamically expanding disk type
- Complete the wizard to create the new VHD or VHDX file
- The virtual disk will now appear in Disk Management for formatting and mounting
This approach allows you to dynamically create virtual disks without needing existing images. You can create disks up to 2TB in size and choose fixed or dynamic allocation modes.
Disk Management Virtual Disk Options
|Legacy virtual disk format compatible with older virtual machines
|Newer virtual disk format supporting larger sizes up to 64TB
|The file size is allocated completely at creation time
|Dynamically expanding disk
|The file size grows as data is added
Using Disk Utility on Mac
The Disk Utility application included with Mac OS provides capabilities to create blank virtual disk images.
To create a virtual hard drive on Mac:
- Open Disk Utility
- Select File > New Image > Blank Image
- Enter a file name and size and select the disk format
- Choose whether to make it a sparse disk image
- Click Save to create the disk image file
- Mount the disk image to access it as a virtual drive
Disk Utility supports compressed and encrypted disk images for added flexibility. Once created, the disk image files can be dynamically mounted as needed to access their contents.
Disk Utility Virtual Disk Options
|Sparse disk image
|Grows in size as data is added to avoid large files
|Compressed disk image
|Uses file compression to save additional space
|Encrypted disk image
|Encrypts the image file contents for security
Creating a Bootable Virtual Hard Drive
In some cases, you may want to create a virtual hard drive that can be used as a bootable startup drive to run an operating system. This allows you to install and run OSes within a virtual machine.
The process for creating a bootable virtual drive is similar to creating a typical data drive, but involves a few additional steps:
- Create a new fixed-size virtual hard drive using Disk Management or Disk Utility
- Format the drive as required by your OS (ex: NTFS for Windows, HFS+ for Mac)
- Mount the virtual drive so it is accessible as a drive letter/volume
- Use imaging software to copy the contents of a bootable OS installer to the drive
- Configure your virtual machine software to boot from the virtual drive
- Start the virtual machine – it should now boot from the virtual OS drive
Once booted, you can install the OS to the virtual drive like you would a physical system. The virtual disk mimics a dedicated startup drive for the VM.
Tips for Bootable Virtual Drives
- Use fixed VHD/VHDX files instead of dynamically expanding for best performance
- Copy an existing OS installer image rather than installing from scratch
- Check for VM compatibility if licensing is a concern (i.e. Windows OS licensing)
- Activate the OS within the VM as you normally would after booting
Enabling Virtual Drives for VM Access
Once you have created a virtual hard drive file, you need to connect it to a virtual machine in order to access and use it. The steps to add a virtual drive will vary depending on your virtualization platform.
Adding Virtual Drives in VMware
For VMware Workstation or VMware Player:
- Edit settings for an existing VM or create a new custom VM
- In VM settings, select the Hardware tab and click Add
- Choose Hard Disk and then select Existing virtual disk
- Browse and select your VHD or VMDK file
- Choose a virtual device node to connect the disk
- Power on the VM and access the new drive
Adding Virtual Drives in VirtualBox
- With VM powered off, go to Settings > Storage
- Under Controller: SATA, click the Add hard disk icon
- Choose Select existing disk and browse your VHD/VDI
- Click OK to add the disk and power on the VM
Adding Virtual Drives in Hyper-V
For Microsoft Hyper-V:
- Shut down the VM if running
- Under Action > Settings, go to the SCSI Controller and select Hard Drive
- Click Add and choose an existing VHDX file
- Adjust the virtual hard disk settings as needed
- Click OK, then start the VM to access the new disk
Working with Data on Virtual Hard Drives
Once attached to a virtual machine, virtual hard drives behave much like physical disks. You can format volumes, copy data, install applications, and otherwise use them like regular drives.
Some tips for working with data on virtual disks:
- Use standard disk formatting tools like File Explorer or Disk Utility to create partitions
- Assign drive letters or mount points to access volumes on the virtual disks
- Use tools like Explorer, Finder, cp, rsync etc. to transfer files
- Install applications directly to virtual drive volumes
- Enable permissions/sharing if needed to allow network access
- Leverage snapshots/revert features to easily rollback changes
Since virtual disks are just files, it’s easy to copy or back them up like any other file in the host OS as well. Overall, aside from some performance differences, virtual disks can be utilized almost identically to physical counterparts.
Virtual Disk Performance Considerations
In some cases, virtual hard drives may provide lower performance than physical disks since all read/write operations are directed through the host OS. Some tips for optimal performance include:
- Use fixed or pre-allocated disk files instead of dynamic disks
- Locate virtual disks on high-performance storage like SSDs
- Use a smaller disk size than assigned RAM for best memory caching
- Enable caching mode or other optimizations in VM settings
- Use VHDX over older VHD format for larger sizes and features
Creating and using virtual hard drives can add storage, improve performance, and enable more flexible computing configurations through virtualization. Key options for creating virtual disks include disk images, tools like Disk Management or Disk Utility, and major virtualization platforms like VMware, VirtualBox, and Hyper-V.
Virtual drives function similar to physical disks once attached to VMs. They can be partitioned, formatted, and utilized just like normal drives but with the benefits of portability and integration with other virtualization features.
By understanding the various virtual disk types and creation methods, you can build customizable systems for data storage, application isolation, and testing environments. Virtualization makes it easy to simulate additional hardware without physical constraints.