Just wondered... is there any larger known RAID56 deployment? I mean something with real-world production systems and ideally many different IO scenarios, failures, pulling disks randomly and perhaps even so many disks that it's also likely to hit something like silent data corruption (on the disk level)?

Has CM already migrated all of Facebook's storage to btrfs RAID56?! ;-) Well at least facebook.com seems till online ;-P *kidding* I mean the good thing in having such a massive production-like environment - especially when it's not just one homogeneous usage pattern - is that it would help to build up quite some trust into the code (once the already known bugs are fixed).