Junichi was wondering about the root device being a logical volume. Jeff said he wasn't sure about d-i doing it. I can personally say that I've performed an install with root on a logical volume using d-i. Been there, done that, got the t-shirt. Whilst it is nice to have everything inside LVM, the downside is, you have to use LILO as your bootloader, and I find GRUB far more flexible. I did such an install a while ago, so it is possible the situation in RC2 or the daily builds is different.