Hmm.. Sometime we upgrade or copy client hosting data stored in /wwwroot/a/abc.com to other partition and we use cp -p option which keep the all permission as it is and then we just change config in httpd.conf and other files...
so -p should do a work but never did upgrade hard disk this way. Other choice is to use Linux LVM; We use Logical Volume Management on a Large System where disk requirment keeps increasing day by day. But for that you need to have LVM on first hard drive ... better solution is as pointed by monk, IMPO.

__________________
Rocky Jr.
What's wrong? I hope I am not making you uncomfortable...

Never send a boy to do a mans job.