vCenter 6.7 VM Server VMDK disks showing larger than the OS Disk itself?

[SamuelC1982]

I have noticed on multiple servers that the VMDK files are bigger than the OS disk itself on the VM. 

For example I have a VM allocated the following disks:

In the OS the following disks are provisioned:

This corresponds with the VM settings in vCenter itself.

So the VMDK for Disk 2 is showing approx. 460GB in size nearly 200GB more than the OS Disk but why?

- No Snapshots

- FTT set to 1

- Running on a VSAN and storage profile set accordingly. 

- VM is Thin provisioned

Any help appreciated for me to understand this discrepancy?

Thanks

Sam

[a_p_]

Moderator Note: Moved to VMware vSAN Discussions 

[TheBobkin · Accepted solution]

@SamuelC1982, This is because they are stored as FTT=1,FTM=RAID1 - a  vmdk provisioned 250GB of space will (if filled) consume 500GB on vsanDatastore (250GB for each mirror).

[TheBobkin]

Additionally, if you fill up a vmdk (e.g. inside the Guest-OS) and then delete the data (again, inside the Guest-OS), it won't automatically release the space written to the vmdk Object, you would have to enable and run TRIM/UNMAP (assuming the vSAN version in use supports this feature) to free up the space.

[SamuelC1982]

Thank you, that answer right in front of me Appreciate it!.