Don't COUNT on being protected from all hungry pests with any type of bag, including a mesh sack. While the mesh sacks do slow down rodents, ravens are able to destroy them and get your food in minutes...and Grand Canyon ravens are notorious! Very smart, very skilled, and very determined, I have seen these birds unzip someone's backpack and root around for food. Not kidding - wish I was.
We have now switched to cookie tins if we must cache our food; if it's just for overnight storage, a good airtight dry bag, hung in a tree (or from a pole stuck into a rock crack if there are no trees around) should be fine against rodents. Ravens don't generally operate at night.
Dave has already seen this, but it's a good warning -- here's what a raven did to my buddy's mesh sack: