You are wrong. Before they used a single git repository for all user repositories in a network. So the git objects in the original repository and all its forks

You are wrong. Before they used a single git repository for all user repositories in a network. So the git objects in the original repository and all its forks were properly deduplicated. Deduplication across different networks does not make much sense. Now, as far as overprovisioning, they had 4 times as much disk space provisioned as necessary: 2 disks in RAID in a single machine times 2 (hot spare). Now they only need 3x, for the three copies.