Forming drives together into a cache hierarchy

[Paul Richards <paul.richards@gmail.com>]

Is there a way to combine a large slow drive with a fast small drive
in such a way that the faster drive simply becomes a cache for the
larger drive?

I imagine a computer where I'd like to have a small fast SSD and a
large but slow spinning disk.  I'd like to put the two block devices
together so that I'm presented with a single logical block device,
where the operating system is using the SSD as a cache (either
inclusive or exclusive, write-though or otherwise) of the spinning
disk.

Is there some magic in LVM that can do this?

If there is nothing at the block device level can it be done at the
filesystem level?

-- 
Paul Richards