vmdk

VMDK stands for Virtual Machine Disk, a file-based disk image format developed by VMware for virtual machines. It is used to provide the storage backing for guest operating systems running on VMware products such as Workstation, Player, ESXi, and vSphere, as well as for transporting disk images between environments. A VMDK image represents a virtual hard disk and may store the data a guest OS writes to its logical drive.

A VMDK image can consist of multiple files. The descriptor file contains metadata about the disk, including size, geometry, disk type, and how data blocks are organized, while the data file holds the actual contents. Some VMDK sets use a single monolithic file, while others separate the descriptor from the data or split data into extents. The format supports both fixed-size disks and dynamically expanding disks that grow as data is written, up to a specified maximum size.

Key features include dynamic expansion, which allows the virtual disk to start small and grow, and fixed-size disks, which allocate the full amount of host storage up front. VMDK images can participate in VMware’s snapshot mechanism, enabling delta disks that capture changes over time. The format also supports various storage layouts and is compatible with cloning and migration workflows within VMware environments.

Interoperability and usage: The VMDK format is closely tied to VMware products but is recognized by a range of third-party virtualization tools and backup solutions. Compatibility and feature support can vary across non-VMware products, and some advanced VMware-specific features may require official VMware implementations to function as intended.