jared, that's about half of the story, as far as i can tell. the issue may be that when doing a block copy, asr doesn't leave any free/slack space on the volume. on SSDs, that may cause degraded performance. on top of that, if you encrypt the whole disk, you effectively map all the blocks, potentially further degrading performance. i haven't seen this in practice myself, but others here with possibly a more discerning eye or more demanding needs have. i'll see if i have any other details in my notes that could be helpful. there are a number of variables, including TRIM support and a bunch of other stuff specific to drive controllers.
