Here’s a clear, concise explanation of what a is in VMware, suitable for a blog post, knowledge base article, or study note. What Is a Flat VMDK File in VMware? In VMware virtualization, a flat VMDK file is one of the two files that make up a raw format virtual disk . It contains the actual raw data written by the virtual machine (VM), stored as a single, contiguous file without metadata or snapshot deltas. Key Characteristics | Feature | Description | |---------|-------------| | File extension | -flat.vmdk | | Content | Raw binary data of the virtual hard disk (sectors 0 to N) | | Format | Monolithic flat – not split into smaller extents | | Metadata | None; metadata is stored separately in a companion .vmdk (small descriptor file) | | Performance | Very high (no extra translation or overhead) | | Sparse support | No – always pre-allocated full size | | Snapshots | Not directly used for snapshot differencing disks | How It Works When you create a virtual disk in VMware, you typically see a single .vmdk file (e.g., myVM.vmdk ). That’s actually a descriptor file – a small text file that points to the real data file, which is named myVM-flat.vmdk .
# List files in VM directory ls -lh /vmfs/volumes/datastore1/myVM/ cat myVM.vmdk Look for line like: RW 41943040 VMFS "myVM-flat.vmdk" Summary The flat VMDK is VMware’s raw, high-performance virtual disk data file, always paired with a small descriptor file. While not as common in modern thin-provisioned environments, it remains important for recovery scenarios, legacy VMs, and maximum I/O performance.