I updated my clients ESX hosts from 6.0U2 to 6.5U1 build 7526125, they have VMWare 6 Essentials. I guess in 6.0U2 there was a bug when trying to change any setting on a VM you would receive a error that there was no room on the datastore. So I updates to ESX 6.5U1 on Thursday. After I updated I powered on the VM and was able to expand the drive with no issues. I need to expand the drive again, but now I am receiving a prompt that "Failed to reconfigure virtual machine (VM Name). The attempted operation cannot be preformed in the current state (Powered on)." the VMDK is thick provisioned with lazily zeroed. The only thing I noticed that was odd is the maximum size is reporting 2.24TB which is the free space left on the datastore. I am use to seeing the Maximum Size being what the current VMDK file size is plus what is free on the datastore.
There are no snapshots for the server and no active backups running, the VM is running Server 2012 R2.
I don't want to have to power off the VM every time I need to expand the drive.
Check manually in the VM folder if any snapshot reside there, Expand the virtual disk, to check it's name... if contains 0000something, than there is a snap. sometimes it won't display in snapshots but files are still there.
What is a guest OS inside your VM? Some old OS may not include drivers for virtual SCSI controller like LSI Logic.
Than if the disk is not bootable disk you can just reattach it to a virtual SCSI controller.
If it's a bootable device you will need to convert your VM using VMware Converter.
Also you can read KB article VMware Knowledge Base