Thanks. Repositories are stored on an ext4 filesystem. I do backups every 12 hours currently. No additional replication is performed but it is something I want to do.
You'll probably want to look into using CEPH/similar when/if the service starts to get busy. Partly for redundancy but also if all your repositories are on a single shared disk you're gonna hit I/O contention if many people are pushing/pulling at the same time - even more so if you get any CI system wired up.
Where are repositories stored and do you use any sort of backup or replication?