VM Datastore Structures

vVols do not change the fundamental VM architecture:

• Every VM has a configuration file (a VMX file) that describes its virtual hardware and special settings
• Every powered-on VM has a swap file.
• Each virtual disk added to a VM is implemented as a storage object that limits guest OS disk capacity.
• Every VM has a memory (vmem) file used to store snapshots of its memory state.

Conventional VM Datastores

Every VM has a home directory that contains information, such as:

Virtual hardware descriptions

Guest operating system version and settings, BIOS configuration, virtual SCSI controllers, virtual NICs, pointers to virtual disks, etc.

Logs

Information used during VM troubleshooting

VMDK files

Files that correspond to the VM’s virtual disks, whether implemented as NFS, VMFS, physical and virtual mode RDMs (Raw Device Mappings), or vVols. VMDK files indicate where the ESXi vSCSI layer should send each virtual disk’s I/O.

For complete list VM home directory contents refer to VMware's documentation that covers Virtual Machine Files.

When a VMware administrator creates a VM based on VMFS or NFS, VMware creates a directory in its home datastore.

With vVol-based VMs, there is no file system, but VMware makes the structure appear to be the same as that of a conventional VM. What occurs internally is quite different, however.

vVol-based VM Datastores

vVol-based VMs use four types of vVols:

• Configuration vVol (usually called “config vVol” one per VM)
• Data vVol (one or more per VM)
• Swap vVol (one per VM)
• Memory vVol (zero, one or more per VM)

The sections that follow describe these four types of vVols and the purposes they serve.