Many projects with many files all uploaded by humans on one server will get messy, by definition. Even if they have a structure, when 1000 of people work on projects there will be made mistakes.
How do big design companies share files?
Do they have a tool to automate this, if so which one?
At my current workplace we use a version control system. To be exact, we use Git + Bitbucket with the LFS (Large File Storage) extension. We also use a graphical diff plugin that lets us see a quick preview of the differences between 2 versions of a given PSD. It does a pretty good job at keeping files safe, knowing who modified what and when, and retrieving previous versions. We ask designers to split their projects as much as possible in order to avoid having to download 2GB of PSD files for a single logo. It doesn't completely solve the problem of having 2 designers work on the same file at the same time and do incompatible changes, but it does make life easier for the most part and help keep the space usage (relatively) low.
"Many projects with many files all uploaded by humans on one server will get messy, by definition."
Not necessarily. I freelanced for a while in a food packaging studio that had other studios around the world. Additionally, they needed to manage a lot of assets (logos, photo shoots, SKUs, etc.) They were pretty much working through FTP but had a very extensive structure. Project IDs, folder structures for the design team and the production team, each file also had an ID section that needed to be edited at every change with project IDs, date of edit, initials of editor, etc. and even how layers should be IDed ordered in the file. But most of all, it was really ingrained in the workplace culture that this was not optional.
I've seen studios (not as big) use other systems like Basecamp. I've never seen projects that involved 1000 of designers... In my part of the world, when a studio hires 20+ people in one location, that's not a huge studio but would qualify as fairly big.
I think that Digital Asset Management Software (DAM) is specifically used for exactly the situation you describe. Here is a nice write-up that explains what DAM is and how it is used.
I haven't worked with a firm that uses a DAM system in a few years; the system I used to use did not have a version control option, but based on my reading, this seems to have improved since then.
There's a number of questions on the subject here as well, this one especially may be useful: Digital asset management software recommendations?
Servers.
But internal local servers which operate essentially like external hard drives, not cloud or internet servers.
If there is a need to share files over the internet, customarily VPN with FTP is used in a closed server environment. This is much different than using public access internet or cloud services. There are IT staff that run things and ensure operation and a very limited number of users, even if that number is in the double or triple digits (it's not in the millions).
There's no "super secret" method in play, just the same methods anyone would use but scaled to meet demand.
Controlling access is more about workflow management than any automation. There are workflow procedures in place to control multiple individuals working on the same thing at the same time. However, common files, such as logos/photos, would be available to everyone at all times.
Even Adobe highly recommends saving files locally, working on them, then uploading to the server again. So, traditionally you would merely mark the server file as being edited, work locally, then replace the server file when done.
I am freelancing for a multinational with alot of multi-language printable items in InDesign, sometimes involving quite large documents with hundreds of linked files. They are working with other in-house designers and outside contractors too for video work and so on. So there is quite a large volume of files set in place on a single FTP account where employees and contractors have access. Everybody is trained on using this and it has been working with no significant issues for many years.
I work for a large retail company in the marketing arm, and we have photo and asset coordinators who catalog and store pertinent files on our local servers. These are tied into a DAM (digital asset management) system that allows for tagging and searching. When it comes to collaborative work we use library items in Adobe CC and version control on certain other file that involve code, as image assets become unwieldy due to how many designers work. We also receive brand and product assets from top athletic companies through their cloud sharing drives and use several hosting platforms that use SSL/FTP for large signage projects and architecture plans.
