When ever a virtual machine accesses a virtual or physical disk
an indirect way.
The virtual machine itself only "sees" a small text file which is a detailed description of the virtual disk.
The VMware program no matter if it is Workstation or ESX then links from this description to the actual data.
This small text file with the extension *.vmdk uses an ini-like format.
It needs no strict syntax - and it does not use section names.
To comment lines use #
Optional parameters and comments can be ommitted.
This ini-like file is stored as human readable plain text-file.
The actual data of a virtual disk is stored in a binary format in a file or directly in a physical disk.
In the description file the VMware program - not the virtual achine - then looks up the path to the actual data.
The actual data can be inside any of this ...
*-flat.vmdk , *-s001.vmdk , *-f001.vmdk , *-delta.vmdk
*.dd , *.img , *.v2i , *.spf
\\.\PhysicalDrive0 , /dev/sda
Most of the different virtual disk types uses the description.vmdk file plus external data stored in various formats.
Only one type - known as "one piece growable" combines both "parts" in one file.
In this case the description in plain text is embedded in the large binary data file.