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Virtual Machine Files and Definitions

Virtual Machine Files and Definitions

As you are likely aware, a virtual machine is made up of a set of files on the storage system. There are a number of different file types that make up a virtual machine, some of which will only be present under certain conditions. Below lists the file types and their functions:

  • VMX – Primary configuration file that stores the virtual machine settings (ie vCPU, Memory, Disks, etc)
  • VMX~ – Change file for original VMX file. Changes are made to the VMX~ first to avoid VMX file corruption (Credit: William Lam)
  • VMX.LCK – Locked VMX file to prevent changes from multiple hosts.
  • VMDK – Virtual machine disk file that stores the contents of the hard drive. Additional drives are appended with a _1, _2, and so on.
  • VMXF – Configuration file for VMs that are in a team (XML file).
  • VMSD – Contains information and metadata regarding snapshots.
  • VMSN – Snapshot state file – stores the running state of the virtual machine when snapshot is taken.
  • <#>.VMDK – Redo-log file created when a VM has at least one snapsho. Stores changes made to a virtual disk while the VM is running.
  • VSWP – Virtual machine swap file created to allow memory over-commitment on a host. Size = Configured Memory Size – Reservation
  • NVRAM – Contains information regarding the BIOS settings for the VM
  • LOG – File to log key VMware activity for troubleshooting purposes
  • HLOG – Log file pertaining to vMotion
  • -AUX.XML – File used to track changes occurring during snapshot activites

 

 Newly created virtual machine on vSphere 5.5:

files-newVM

Files from a newly created VM

 

Single snapshot of server shown above:

files-newSnap

Files after new Snapshot

 

Below shows two attached drives, one of which is 40GB thick provisioned and the other is thin provisioned:

files-ThickVsThin

Below shows additional files that are created when the VM is powered on, most notably the files surrounding memory functions for the VM:

files-PowerOnVM

 

About The Author

Bryan Krausen

Bryan Krausen is currently working as a Sr. Solutions Architect with experience in a vast number of platforms, specializing in AWS and HashiCorp tools.

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