Add a second disk to system using vagrant

Vagrantfile

config.vm.provider "virtualbox" do |v|
  file_to_disk = './tmp/large_disk.vdi'
  unless File.exist?(file_to_disk)
    v.customize ['createhd', '--filename', file_to_disk, '--size', 500] # size is in MB
  end
  v.customize ['storageattach', :id, '--storagectl', 'SATAController', '--port', 1, '--device', 0, '--type', 'hdd', '--medium', file_to_disk]
end

don't forget to vagrant reload after!