Q:

Move Web Directory to Raid Array

I want to improve the performance of a web application running on Apache, so I created a Raid Array on /dev/md0. 
Now I need to figure out how to move the application to the array and make sure that Apache will still serve it when someone accesses my domain. 

Web application is in the directory: /var/www/html - Raid Array device
  is: /dev/md0

How do I make the application run on the array?

A:

Try this:
# cd /var/www
# mv html old-html
# mkdir -m755 html
# mount /dev/md0 html
# cp -pr old-html/* html

That should mirror the current contents of /var/www/html onto the RAID array.
Some notes:

The mount command might need tweaking, and ultimately you will want to have an entry in /etc/fstab for it. I assume whatever guide you're using to set up the RAID array has got the correct mount and fstab info.
The permissions on /var/www/html are simply what I have here. You might need to adjust them to match your site's existing perms.
The cp command won't copy dotfiles at the top level of your site. If for some strange reason you have a top-level .htaccess file, for example, instead of having the root site config in /etc/httpd somewhere, you'll have to copy that file over by hand. (I could have given you a more complex command that would copy top-level dotfiles, too, but there seems little point.)

