Ian Paul has a good post here related to interpreting the six water jars in the water to wine sign of John 2:6. I especially appreciate his recognition of the historical veracity of John's Gospel.
But I would add that one needs to wrestle with why the author mentions that the jars were made of stone and why there were six of them. If one simply wanted to relay the miracle of water to wine, then the author could have said there were several water jars and still conveyed the basic essence of the story. As good writers know, the inclusion or exclusion of details can make or break a story. Too many or too few can have a negative impact on the story.
The details for me echo creation and Genesis 1–2. For example, the similarity of John 1:1 to Genesis 1:1 sets things up, the reference to “day” (2:1), the reference to water (Gen 1:2), the number six (six days of creation), the stone vessels representing purity echoing the repeated refrain of “good” or “very good,” the presence of God implied in the first “marriage” (Gen 2:22-24), the fact that speech is involved in the creative act (2:5, 7, 8) as it is in Genesis (“and God said,” ) suggest to me that there are intended allusions to creation and Genesis 1–2. And creation is a divine prerogative. As such, this dovetails with the author stated purpose that his readers might know that Jesus is “the Son of God” (20:31).