I'm running ESXi 6.0u2 free. I've got a 54TB datastore on DAS to an LSI SAS3 controller (9380-4i4e). After setting everything up, including a Server 2012 R2 standard VM, I was able to create a 30TB VMDK for the server, though I had to use the web client to do it (the fat client seems to only allow 16TB max).
At some point I lost the ability to edit ANY settings on that VM (memory, CPU, disk, etc) and it throws the error in the subject line. Again, even if I'm trying to change a non-disk-related setting. I removed (and deleted) the entire datastore and recreated it from scratch and I'm having the same issue. In the web client it even shows it has 54TB free/available.
I've also got a Windows 7 x64 pro and a Windows 10 x64 pro VM running and I'm having the same problem with editing their settings in the web client as well. I was having no issues earlier today however. I did find that I was able to create a new virtual disk of 16TB on the Windows 7 VM using the vSphere client, even though it appeared to throw an error it still worked. Problem is it appears you need the web client to do anything over 16TB which is what I need to do and its basically unusable at this point.
Note that I can still edit VM settings using the vSphere client as normal. I just can't edit settings on ANY VMs using the web client? I already tried the "Reset client settings" in the web client; didn't help.
I've seen only a couple other folks online that have run in to this and I see no fix. I'm trying to backtrack my steps and the last thing I was doing was messing around with MTU settings on my vSwitch in the web client. This definitely feels like a bug but I'm not sure how to proceed! Maybe there's some way to completely reset/reinstall the web client?