> They keep every project in a single repo, mystery solved.

This kind of "Duh, look what you're doing" response isn't really justified.

Sure, splitting up your repository would make things faster, but having to maintain multiple repositories is a major headache for the end-users of git. If it's possible, why not fix its scalability so that you don't have to worry about it?

I'm pretty sure that cloning a repository of that size can't be all that fun.

You tend to split repositories based on team responsibilities. I doubt that every developer needs access to update all million+ files.

What this comes down to is that they've made certain architecture decisions that ideally would be changed but it's not possible to do so at this time.

I agree. Users are always right, even for open source software. Requiring the users to change their way is an easy way to lose them. A major player like Facebook willing to use Git is a good thing, as it may help spread the software in companies like Facebook. Git should try its best to please its user, rather than the other way round.

Git submodules make it really easy to split up large projects into smaller components.

Also, as Ævar writes in the first response, "there's only so much you can do about stat-ing 1.3 million files".

> They keep every project in a single repo, mystery solved.

That's not true:

> It is based on a growth model of two of our current repositories (I.e., it's not a perforce import). We already have some of the easily separable projects in separate repositories, like HPHP. If we could split our largest repos into multiple ones, that would help the scaling issue. However, the code in those repos is rather interdependent and we believe it'd hurt more than help to split it up, at least for the medium-term future.

They already have multiple repositories, the stats they're doing there is based on "two of [their] current repositories" implying more than two.

Why would he take HPHP as an example then? It should be obvious that there is not much interdependence with the other code.

Sounds to me like this: http://thedailywtf.com/Articles/Enterprise-Dependency-Big-Ba...

He most likely used HPHP as an example because the message he was replying to also mentioned HPHP. At least that's how I interpreted it.

I'd imagine Facebook's developers are better than that.