title: How can I simulate a failed disk during testing?
body: <p>In a Linux VM (Vmware workstation or similar), how can I simulate a failure on a previously working disc?</p>
  
  <p>I have a situation happening in production where a disc fails (probably a controller, cable or firmware problem). Obviously this is not predictable or reproducible, I want to test my monitoring to ensure that it alerts correctly.</p>
  
  <p>I'd ideally like to be able to simulate a situation where it fails writes but succeeds reads, as well as a complete failure, i.e. the scsi interface reports errors back to the kernel.</p>