Good job on the clear outline Neil, but there's a fundamental issue which worries me.
Has anyone actually shown that Fusion Drive works? Not that you can create a Fusion drive, we know that. But does it reliably do what everyone thinks it does?
When you put more data on there than will fit on the SSD you'll see it slow down as it starts using the HDD. But then when you repeatedly access data which is on the HDD has anyone shown that it gets migrated to the SSD?
I have seen a few tests so far that show that it
doesn't and lots that don't show anything useful.
Maybe it works but what's the key to get the migration happening? Haven't seen it yet.
Has anyone been able to recover data from a crashed system? Repair the filesystem? I've seen some simple tests that produces fatal errors (as in blow all your data away and start again). This does not induce comfort.
For now I'll stick with separate SSD and HDD disks and put the data on each that needs to be on each.
I'm happy for you guys to experiment and be on the bleeding edge (presumably on systems you're not depending on for work) but be prepared for some pain. I'm just sayin'...
<Wanders off muttering about barge poles...>