Welcome to the Community,
Please provide some details about the storage and the datastore size.
- What's the current size and what's the size of the underlying LUN?
- What's the VMFS version of the datastore (VMFS3 or VMFS5)?
- What type of storage do you use (local/shared)?
Increasing the local datastore on the ESXi installation disk is not supported in the GUI and you may need to do this manually from the command line.
André