Yes. And another benefit of /usr vs / was that is was simpler to read only mount /usr than r/o mount /.
Why do you want to do that? Well, when you have a machine with virtualization you can share the /usr partition across all instances, physically. Which makes a lot of sense if you want to virtualize hundreds of Linux guests on one physical box: you memory map the /usr partition in hypervisor ram, you share that ram across all guests and wham you have snappy fast virtual machines with low physical footprint.
That was actually done, e.g. on IBM mainframes running "your personal web server" for thousands of users in one single mainframe. Fun times.
And only when the root partition could also be mounted r/o, with just an individual /etc, and when large partitions became doable as /, only then it started to make sense to abandon /usr
> Why do you want to do that? Well, when you have a machine with virtualization you can share the /usr partition across all instances, physically.
Or you could share the whole /usr over NFS to hundreds of diskless workstations, each having their own separate / (also shared over NFS). Remember that disk space was expensive back then; having hundreds of identical copies of the large /usr tree on the NFS server would be a huge waste.
Why do you want to do that? Well, when you have a machine with virtualization you can share the /usr partition across all instances, physically. Which makes a lot of sense if you want to virtualize hundreds of Linux guests on one physical box: you memory map the /usr partition in hypervisor ram, you share that ram across all guests and wham you have snappy fast virtual machines with low physical footprint.
That was actually done, e.g. on IBM mainframes running "your personal web server" for thousands of users in one single mainframe. Fun times.
And only when the root partition could also be mounted r/o, with just an individual /etc, and when large partitions became doable as /, only then it started to make sense to abandon /usr
The split made lots of sense back in the days.