thoxahr

Blood contains immune system elements which would likely reject cancer samples from a different donor. Having to obtain blood and cancer sample from the same donor would complicate things quite a bit.

In addition, it doesn't seem as though they are able to recycle the medium. Frequently draining and refilling with fresh blood seems rather wasteful.

The similarly named "dm" (device mapper) is a generic abstract block layer tool. md is still specifically a software raid implementation.