I don’t think that CEPH would outperform GlusterFS unless you are using SSD, and I think the idea AlexanderR is thinking about is using big old fashioned rotating hard disks. I like the idea if you have many TB of data and want to easily expand the backup storage.
We have around 170TB data, and I can see this as a good solution for backup storage, I would also like to know if anyone have tried this or if it works.