Online filesystem scrubbing and repair

Just today I had to reboot to a rescue system to btrfsck my desktop's root file system to fix my btrfs send/receive based backup. It's not that big a deal, but having to reboot sucks. Especially when the machine is also the only source of music :)

Btw. btrfs send/receive seems to be a very good detector for file system errors.

At work we of course have redundant failover clusters. But those only help for hardware issues (including faulty storage). When there's a file system error in one of the data volumes, all we can do is to take the service offline for fsck. If it's a major breakage we can restore one of the hourly backups, but the first try will always be to salvage everything.