quoted

If you have a temporary space for your data, I'd suggest you move it
out and go for an internal bitmap solution. It certainly beats the
patch work you're going to have to do on the startup scripts (and
every time you update mdadm, or the distro).

There should be no need to move the data off - you can add an internal
bitmap using the --grow option.  An internal bitmap does have more of an
overhead than an external one though.

	I thought I remembered reading in the man page than an internal
bitmap could only be added when the array was created?  Is that incorrect?