You will be reinventing the wheel; that's part of working with open source on big sites. There just isn't one open-source deployment/backup/versioning/etc system out there. Nearly every large deployment/backup/versioning/etc system i've seen has been custom. Most of these details will be specific to the group you're working with and the project's requirements.
Don't worry so much about getting the process right or finding a pre-packaged solution. The most common solutions will be the same old tools re-worked and customized to get the job done on that site. I'd say the best thing you can do is put your fingers into every single open-source pie you can and get a feel for it all. The rest is a natural evolution of developing for your target platform.
