Is there any way to run GlusterFS in a replicated mode, but with the ability to dynamically scale the volume up and down?

Say you have 3 servers all running glusterd. your Gluster volume would have to be setup with replica 3

gluster volume create test-volume replica 3 192.168.0.150:/test-volume
192.168.0.151:/test-volume 192.168.0.152:/test-volume

You would then mount it as say \mnt\gfs_test

What happens when I want to add 2 more servers to the storage pool and then also use them in this volume? Is there any easy way to expand the volume AND increase that replica count to 5?

My end goal is to run this on EC2 instances, say 3 Apache front ends, with the webroot setup on the gluster volume mount. My concern is that if I ever need to spin up a server, I would want the server to not only be an additional Apache front end, but also another server in the gluster file system, adding to fault tolerance as well as possibly giving a slight boost in read speed.

Maybe there are better options that would fit the bill here?

Thanks.