> Some are at 20k+ users so they are close to needing something like Ceph
Or they will scale it themselves ala Alibaba: http://www.slideshare.net/MinqiPan/how-we-scaled-git-lab-for... . They appear to have written a libgit2 backend for their object store(among other things).
I don't see a good reason why solutions using different storage backends could not make it into the OSS project. Many companies run their own Swift cluster, which is OSS.
If you're using CephFS and everyone else wants to be using other Cloud storage solutions, that would actually put you at a disconnect with your users and leave room for a competitor with the tools and experience to scale out on Cloud storage to come in offering support. I would at least consider all the opinions in this thread and maybe reach out to that Minqi Pan fellow from Alibaba with questions..
I actually really like GitLab and wish we could be using it at my company; this is why I'm spending so much effort on this topic(and scaling git is interesting). Hopefully my opinions are not out of place.