Here's my patch to give morph hardlink chroots.
My branch is "joeburmeister/hardlink-chroots"
Here's the time results of building a complete devel-system image on my
virtual machine, with and without.
original: real 5h 17m 47s
Hardlink: real 2h 52m 27s
Unionfs-fuse: real 3h 18m 51s
I think we should look at in-kernel unionfs chroots still because it
would be less disk writes, good for SSDs. But for the time being
hardlinks are less writes then we are doing now, and much faster.