"Important: CephFS currently lacks a robust ‘fsck’ check and repair function. Please use caution when storing important data as the disaster recovery tools are still under development. For more information about using CephFS today, see CephFS for early adopters."
I'm getting the same feeling I get when I'm watching those "Hold my beer and watch this..." videos.
From my vantage point they look to have 0 experience in building and running infrastructure... and asking advice on HN. They might ask well post a Ask Slashdot thread if they want armchair advice. Genuinely, I think they've crunched some numbers and think they can run their stuff cheaper and faster in-house... but probably underestimated the human-experience angle.
For just 10-20 physical servers, this is going to be either extremely expensive (if they hire right) or extremely painful (if they don't).