The biggest subsystem vendor that uses redirect on write is NetApp because
they offer the write anywhere file layout, WAFL.
Because they don’t care where they write data in the first place, as soon as
they’ve got enough blocks they write a stripe. They allocate space on their
disk differently to the traditional block I/O vendors.
In the exam it wont differentiate between Copy on Write or Redirect on Write
(it will assume Copy on Write).