Disable hostiocache in Virtualbox for better performance

Vagrantfile

# -*- mode: ruby -*-
# vi: set ft=ruby :

# Vagrantfile API/syntax version. Don't touch unless you know what you're doing!
VAGRANTFILE_API_VERSION = "2"

Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
  config.vm.box = "coreos"

  config.vm.provider "virtualbox" do |v|
    v.memory = 256
    v.customize ["storagectl", :id, "--name", "IDE Controller", "--hostiocache","off"]
  end
end