Is VMDK same as ISO?

VMDK and ISO are two common virtual machine disk formats used in virtualization. While they serve a similar purpose, there are some key differences between the two formats.

In short, VMDK refers to Virtual Machine Disk format used by VMware virtualization products. ISO refers to the optical disc image format based on ISO 9660 file system standard. An ISO image contains an exact copy of data from the optical disc, including the file system, structure and data.

Some quick answers upfront – VMDK and ISO formats are not the same. VMDK is a virtual hard disk file used by VMware products to represent a virtual machine’s hard disk. ISO is an industry standard format to represent an exact copy of optical media like CD or DVD. While VMDK contains a virtual hard disk with OS and applications, an ISO contains the installer files for OS or applications.

What is VMDK?

VMDK stands for Virtual Machine Disk. It is a file format used by VMware virtualization products such as VMware Workstation, ESXi and vSphere to represent a virtual machine’s hard disk.

VMDK allows encapsulating an entire operating system, applications and data into a single file for convenient deployment, management and backups of virtual machines. VMDK files contain a virtual hard disk with guest OS, apps, data files and other configs needed to boot and run a VM.

Some key characteristics of VMDK file format:

– Developed by VMware for their virtualization products.
– Used to represent a virtual hard disk for guest OS and apps.
– Allows mounting the VMDK on VMware virtual machines to boot and run the guest OS.
– Supports adding multiple virtual disks in layered approach.
– Capabilities like snapshots, cloning, thin provisioning.
– Portability across VMware products like Workstation, vSphere, Fusion etc.

In summary, VMDK serves as a virtual hard disk containing the guest operating system, applications, data files and configuration of a virtual machine. It allows convenient deployment, portability and management of VMs on VMware virtualized platforms.

VMDK File Types

VMDK files come in two variants:

– Monolithic VMDK – The virtual disk is stored as a single VMDK file which contains the entire hard disk data. This allows easier portability of VM across hosts.

– Split VMDK – The virtual disk data is stored across multiple VMDK files for performance and management benefits. Includes descriptor file pointing to multiple data files storing chunks of the VMDK.

VMDK Advantages

Some benefits of using VMDK for virtual machine disks:

– Portability – VMDK can be easily copied, moved and deployed across VMware platforms.

– Performance – Split VMDK allows faster reads and writes to virtual disk.

– Management – VMDK allows snapshots, cloning, backups and thin provisioning of VMs.

– Access Control – VMDK allows setting access permissions on virtual machine files.

– Scalability – VMDK images can be expanded on the fly to add more storage.

– Compatibility – VMDK is supported across all VMware virtualization platforms.

In summary, VMDK provides an efficient format to bundle and manage virtual machine storage in VMware environments.

What is ISO?

ISO refers to the ISO 9660 file system standard for optical disc image format. It is commonly used for CD, DVD and Blu-ray discs.

ISO format provides specifications to store data on optical media in a structured format across operating systems. The key aspects are:

– ISO defines a file system for optical media like CD, DVD, Blu-ray discs.

– It provides specifications for file system attributes like file names, folder structures, file size, permissions etc.

– The standard aims for OS independence and cross platform compatibility.

– The file system is read-only and designed for easy distribution of data.

– Widely adopted industry standard supported on all operating systems.

– Allows exact bit-stream copies of optical discs in a single file – called ISO image.

In summary, ISO 9660 provides a vendor-neutral file system to store structured data on optical media, enabling interchange across platforms.

ISO Image Files

An ISO image file contains an exact sector-by-sector copy of the data on an optical disc like CD, DVD, stored in ISO 9660 format.

Key properties of ISO image files are:

– Contains full content of the optical disc like CD/DVD – data, file system, bootable info etc.

– Has .iso extension.

– Used for archiving and distributing optical disc data like OS installers.

– Can be mounted as virtual drives on supported OS for access to data.

– Useful for bootable media like OS installation DVDs.

– Supported across operating systems – Windows, Linux, macOS etc.

In summary, ISO image files allow efficient redistribution of optical media in a single file across computing platforms.

Differences Between VMDK and ISO

While VMDK and ISO formats both relate to virtual disks and optical media, there are some key differences:

Storage Contents

– VMDK contains a virtual hard disk with complete guest OS, apps, data and configs to boot a VM.

– ISO contains installer files and bootable data to install or boot into an OS, rather than an actual OS.


– VMDK is attached to a VM to run the guest OS and applications directly.

– ISO allows installing or booting into secondary environments like guest OS or rescue tools.

Access Type

– VMDK provides full read-write access to the virtual disk to run the guest OS.

– ISO images are usually read-only and used for installation purposes.

Platform Support

– VMDK is proprietary to VMware virtualization products.

– ISO is an open standard supported across platforms.


– VMDK files can be easily moved between VMware products.

– ISO files can be used across all operating systems – Windows, Linux, macOS etc.

Property VMDK ISO
Full Form Virtual Machine Disk ISO 9660 Optical Disk Image
Contents Virtual hard disk with guest OS, apps, data Bootable media, installer files
Primary Use Run guest OS directly Install or boot into secondary environments
Access Type Read-write Usually read-only
Platform Support VMware virtualization Cross-platform standard

In summary, while VMDK and ISO are disk image formats, VMDK represents an actual virtual hard disk while ISO represents installer media for operating systems. Their usage, access types and platform support differs.

Converting Between VMDK and ISO

While VMDK and ISO serve different purposes, it is possible to convert between the two formats:

– Converting VMDK to ISO: The VMDK virtual disk can be mounted as a drive and files can copied over to an ISO image.

– Converting ISO to VMDK: Requires creating a new blank VMDK, attaching ISO as CD-ROM, installing OS/apps from ISO to VMDK.

However, a direct conversion is not possible since the formats store different contents – VMDK holds an OS volume while ISO contains bootable installer files.

Some tools that allow VMDK and ISO conversion:

– VMware vCenter Converter
– StarWind V2V Converter
– WinImage
– PowerISO

The conversion may require modifications and drivers to make the new image bootable. The fidelity when converting between the formats depends on the tool used.

In summary, VMDK and ISO contain different types of data, so direct format conversion is not straightforward. Using a third-party tool can allow converting between VMDK and ISO by transferring data via an intermediate mount or attach.


While VMDK and ISO formats both relate to virtual machine disks and optical media, they serve different purposes.

Key differences:

– VMDK represents an actual virtual hard disk containing installed OS, apps, data. ISO contains bootable installer files for OS or apps.

– VMDK allows full read-write access, ISO images are usually read-only.

– VMDK is a VMware proprietary format, ISO is an open standard.

– VMDK provides portability across VMware platforms, ISO provides cross-platform compatibility.

– Direct conversion between formats is not straightforward due to different contents. Requires tools to copy data between mounted images.

In summary, VMDK and ISO formats are not the same. VMDK represents a virtual machine hard disk while ISO represents optical media installer images. The formats have differing usage scenarios, platform support and conversion capabilities.