Hmmm, digging some further, not all seems well.
I created a new vm on the datastore:
-rw------- 1 nobody nogroup 2147483648 Feb 10 23:39 test_0-flat.vmdk
-rw------- 1 nobody nogroup 492 Feb 10 23:39 test_0.vmdk
-rw-r--r-- 1 nobody nogroup 0 Jan 2 1980 test.vmsd
-rwxr-xr-- 1 nobody nogroup 2009 Feb 10 23:40 test.vmx
-rw-r--r-- 1 nobody nogroup 52502 Feb 10 23:40 vmware.log
so the files are on the ubuntu server.
Starting the vm however fails, the vmware.log of the vm:
2017-02-10T22:34:48.827Z| vmx| I125: DISK: OPEN scsi0:0 '/vmfs/volumes/18630e34-de98dd50-0000-000000000000/test/test_0.vmdk' persistent R[]
2017-02-10T22:34:48.831Z| vmx| I125: DISKLIB-VMFS : VmfsExtentCommonOpen: possible extent truncation (?) realSize is 0, size in descriptor 4194304.
2017-02-10T22:34:48.831Z| vmx| I125: DISKLIB-VMFS : "/vmfs/volumes/18630e34-de98dd50-0000-000000000000/test/test_0-flat.vmdk" : failed to open (The file specified is not a virtual disk): Size of extent in descriptor file larger than real size. Type 3
2017-02-10T22:34:48.831Z| vmx| I125: DISKLIB-LINK : "/vmfs/volumes/18630e34-de98dd50-0000-000000000000/test/test_0.vmdk" : failed to open (The file specified is not a virtual disk).
2017-02-10T22:34:48.831Z| vmx| I125: DISKLIB-CHAIN : "/vmfs/volumes/18630e34-de98dd50-0000-000000000000/test/test_0.vmdk" : failed to open (The file specified is not a virtual disk).
2017-02-10T22:34:48.831Z| vmx| I125: DISKLIB-LIB : Failed to open '/vmfs/volumes/18630e34-de98dd50-0000-000000000000/test/test_0.vmdk' with flags 0xa The file specified is not a virtual disk (15).
2017-02-10T22:34:48.831Z| vmx| I125: DISK: Cannot open disk '/vmfs/volumes/18630e34-de98dd50-0000-000000000000/test/test_0.vmdk': The file specified is not a virtual disk (15).
2017-02-10T22:34:48.831Z| vmx| I125: DISK: Opening disks took 5 ms.
2017-02-10T22:34:48.831Z| vmx| I125: Module 'Disk' power on failed.
2017-02-10T22:34:48.831Z| vmx| I125: VMX_PowerOn: ModuleTable_PowerOn = 0
2017-02-10T22:34:48.831Z| vmx| I125: SVMotion_PowerOff: Not running Storage vMotion. Nothing to do
2017-02-10T22:34:48.833Z| vmx| I125: Vix: [90009 mainDispatch.c:1175]: VMAutomationPowerOff: Powering off.
2017-02-10T22:34:48.834Z| vmx| W115: /vmfs/volumes/18630e34-de98dd50-0000-000000000000/test/test.vmx: Cannot remove symlink /var/run/vmware/0/80444906393_90009/configFile: No such file or directory
2017-02-10T22:34:48.834Z| vmx| I125: WORKER: asyncOps=1 maxActiveOps=1 maxPending=0 maxCompleted=0
2017-02-10T22:34:48.839Z| vmx| I125: Vix: [90009 mainDispatch.c:4234]: VMAutomation_ReportPowerOpFinished: statevar=1, newAppState=1873, success=1 additionalError=0
2017-02-10T22:34:48.839Z| vmx| I125:
2017-02-10T22:34:48.839Z| vmx| I125+ Power on failure messages: File system specific implementation of LookupAndOpen[file] failed
2017-02-10T22:34:48.839Z| vmx| I125+ File system specific implementation of LookupAndOpen[file] failed
2017-02-10T22:34:48.839Z| vmx| I125+ File system specific implementation of LookupAndOpen[file] failed
2017-02-10T22:34:48.839Z| vmx| I125+ The file specified is not a virtual disk
2017-02-10T22:34:48.839Z| vmx| I125+ Cannot open the disk '/vmfs/volumes/18630e34-de98dd50-0000-000000000000/test/test_0.vmdk' or one of the snapshot disks it depends on.
2017-02-10T22:34:48.839Z| vmx| I125+ Module 'Disk' power on failed.
2017-02-10T22:34:48.839Z| vmx| I125+ Failed to start the virtual machine.