Interesting that at St. Vladimir's Seminary in my OT class we just addressed this!
Really the Orthodox response to creationism vs. evolution is: It doesn't make sense to argue one way or the other.
The Orthodox Church follows a homiletic reading of Genesis which means: Genesis exists to form you as a follower of God and that is its purpose. To argue about whether it is literal or allegorical misses the point and gets you bogged down in nonsese. God created the heavens and the earth. Wow! Isn't that amazing! So make sure you stay free from sin!
You can believe in a literal 6 days or not; it's not dogmatized. But in the end you have to rise above that level to the homiletic level.
The best patristic source on this in my opinion is St. Basil in his "Nine Homilies on the Hexameron" available at www.newadvent.org
in the Church Fathers section. You'll have to read his views on science and creation to understand more fully what I am saying (because I am not always clear!)