VHD to VMDK performance is identical to a native VMDK when properly converted. VMware Workstation converts the disk to a fully native VMDK format during the process. It does not run the VHD through a translation layer. All snapshot, thin provisioning, and I/O features work exactly as they would on a disk originally created as VMDK. This means you can proceed without worrying about hidden performance costs or feature limitations. The final result is indistinguishable from a disk you created directly in the VMware environment.
What actually happens during VHD to VMDK conversion
When you use VMware Workstation’s built-in conversion tool, the software reads the source VHD file’s data blocks. It writes them into a new, fully native VMDK file. This process is a true format transformation, not a wrapper or emulation layer. The resulting VMDK uses the same on-disk structure, metadata layout, and block allocation as any VMDK created natively by the application. For example, if the source VHD was a fixed-size disk, the converter creates a pre-allocated VMDK. If the VHD was dynamic, the converter produces a thin-provisioned VMDK by default. The tool also handles partition tables and file systems transparently. It preserves the exact byte order and geometry. Because the output is a standard VMDK, the VMware hypervisor treats it exactly like any other virtual disk. No translation or runtime overhead occurs during VM execution.
VHD is one of the virtual disk formats that VMware Workstation converts to a fully native VMDK without a translation layer.
When performance problems do occur
Performance issues arise only when users skip the transformation step. If you attempt to mount a VHD directly using a third-party utility or by attaching it via nested virtualization, the hypervisor must interpret the VHD container format on the fly. This introduces significant I/O overhead, with slower throughput in benchmarks. It also breaks snapshot chains, as VMware cannot parse VHD differencing blocks. A common mistake is trying to use a VHD in VMware Workstation by adding the .vhd file directly to a virtual machine’s storage controller. The program will error out with “Invalid disk format” or “Failed to open disk.” The correct workflow is always to convert first. Similarly, if you need to setup a network in vmware workstation, the transformed disk behaves identically to a native VMDK. Network performance is unaffected by the disk format.
Snapshots and advanced features after conversion
After the change, the VMDK supports every native VMware feature without restriction. You can take snapshots, including incremental snapshots. The snapshot chain works exactly as it would on a disk created from scratch. Thin provisioning remains fully functional. The VMDK grows on demand as you write data, and you can reclaim space using VMware’s shrink or compact tools. Differencing disks, also known as linked clones, also work because the converted VMDK is a base disk that can parent child disks. For example, if you want to make a VM from your physical machine using VMware Workstation, you would first convert the physical disk to VMDK. You can then use that VMDK as a base for clones or snapshots. Finally, if you later need to use a VMDK file in VMware Workstation on a different host, the transformed disk is portable to any VMware product. It works in Fusion or ESXi without re-conversion. The only limitation is that the tool cannot preserve VHD-specific metadata like Hyper-V’s generation ID. However, this has no impact on performance or snapshot functionality within VMware Workstation.
