VMDK Files

These are the disk files that are created for each virtual hard drive in your VM. There are 3 different types of files that use the vmdk extension, they are:

• *–flat.vmdk file – This is the actual raw disk file that is created for each virtual hard drive. Almost all of a .vmdk file’s content is the virtual machine’s data, with a small portion allotted to virtual machine overhead. This file will be roughly the same size as your virtual hard drive.

• *.vmdk file – This isn’t the file containing the raw data anymore. Instead it is the disk descriptor file which describes the size and geometry of the virtual disk file. This file is in text format and contains the name of the –flat.vmdk file for which it is associated with and also the hard drive adapter type, drive sectors, heads and cylinders, etc. One of these files will exist for each virtual hard drive that is assigned to your virtual machine. You can tell which –flat.vmdk file it is associated with by opening the file and looking at the Extent Description field.

• *–delta.vmdk file – This is the differential file created when you take a snapshot of a VM (also known as REDO log). When you snapshot a VM it stops writing to the base vmdk and starts writing changes to the snapshot delta file. The snapshot delta will initially be small and then start growing as changes are made to the base vmdk file, The delta file is a bitmap of the changes to the base vmdk thus is can never grow larger than the base vmdk. A delta file will be created for each snapshot that you create for a VM. These files are automatically deleted when the snapshot is deleted or reverted in snapshot manage