Never try to rename a -flat.vmdk file directly. If you do, the descriptor file (the small .vmdk ) will no longer point to the correct filename, and your VM will fail to power on with an error like "The parent virtual disk has been modified."
: This is the "muscle." It contains the actual raw data of the virtual machine. When you provision a 100GB disk, this is the file that stores those 100GB of files, operating system data, and applications. Broadcom Community +3 Why Is It "Flat"? The term "flat" refers to the pre-allocated nature of the disk. Unlike "sparse" disks (which grow only as you add data), a flat disk is usually mapped out as a continuous block of space on the physical datastore. This design is optimized for performance, making it the standard for enterprise-level virtualization on ESXi. NAKIVO +1 The "Hidden" File Mystery One common point of confusion is that when using the
: The flat file contains strictly raw data; it has no headers or metadata. All configuration details (like disk geometry or hardware version) are stored separately in the descriptor file . The Descriptor vs. Flat File Relationship vmware flat file
[ vSphere vCenter View ] ---> Displays a single "Virtual Disk" icon | +---> [ ESXi Shell / File System ] | +---> VM_Name.vmdk (Text Descriptor / Map) +---> VM_Name-flat.vmdk (Raw Binary Data Block) Key Technical Characteristics 1. Pre-Allocated Storage Footprint
: A raw, pre-allocated binary extent. This hidden giant stores the actual guest operating system, application files, and production data. Never try to rename a -flat
Occasionally, a descriptor file gets corrupted or deleted, leaving you with an orphaned -flat.vmdk . Without the descriptor, VMware cannot mount the disk.
For many administrators, this can be confusing. Which one is the actual virtual disk? Do you need both? Broadcom Community +3 Why Is It "Flat"
Here is a breakdown of what the flat file is, why it is critical, and how it relates to your VM’s storage.
You can recreate the descriptor file manually or by using vmkfstools .
In VMware virtualization, a "flat file" typically refers to the file, which is the raw disk data file for a virtual machine (VM). Unlike the descriptive .vmdk file (a small text header), the flat file contains the actual binary data written to the virtual disk.
myVM.vmdk (descriptor – text) myVM-flat.vmdk (actual disk data – binary)