I think my draft is more detailed: https://wiki.archlinux.org/title/User:Foxboron/GitMigration
EDIT: I realized the DeveloperWiki is my rewriting the above draft, but it contains somewhat less details of the implementation. I never really rewrote it it seems.
Runbook for the migration can be found here: https://md.archlinux.org/utjjQ-bQTsipIKntPrpf8g?both
The btrfs raid setup is standardized across all our infra and can be found on ansible.
https://gitlab.archlinux.org/archlinux/infrastructure/-/blob...
https://gitlab.archlinux.org/archlinux/infrastructure/-/blob...
From what I can tell it's been working fine and behaves nicely with failing disks.
Github usage predates the Gitlab instance and some projects haven't been migrated. We also keep some repositories on Github as a secondary mirror.
We've also had some performance issues on Gitlab for `svntogit` repository because of weird branch structures. However this repo is not deprecated so it doesn't matter anymore.