1. A method of determining features of a logical block device for a computer system, comprising: querying the logical block device with a first query and receiving a response thereto from the logical block device that indicates whether or not the logical block device is thinly provisioned; and querying the logical block device with a second query and receiving a response thereto from the logical block device that indicates whether or not the logical block device supports an unmap command, wherein the unmap command is a command to deallocate blocks previously allocated to the logical block device.