Quick steps to expand a 2TB VMFS3 datastore to >2TB with vSphere5
VMFS3 datastore, ~2TB on a 3.6TB LUN
Click “Upgrade to VMFS5”
Note that the next window will look much different if <5.x hosts are connected.
To expand the datastore, right-click and select properties.
Click Increase to launch a wizard, which I’ll skip for today – it’s the same as earlier versions.
After the GUI you’ll see the new size listed.