> For that you need to run btrfs-check, and that can only be done offline. You almost never want to run btrfs-check. In itself, Btrfs is fairly "self healing",

> For that you need to run btrfs-check, and that can only be done offline. You almost never want to run btrfs-check. In itself, Btrfs is fairly "self healing", and only if you run into "weird things" in the log like invalid index files should you run check, and almost certainly never with the --repair option. The thing about Btrfs (and ZFS) is that it is Copy-on-Write, and as such, new data is written to an unused part of the filesystem. It doesn't need to modify structures of existing data, thereby reducing the risk of bad metadata. A file in Btrfs is either written or it is not. If a power outage occurs after a file has been written, but before the metadata is updated, the file is not written, and in case you're updating a file, the old file is still preserved. If a crash occurs while writing metadata, Btrfs has multiple copies of metadata, and is able to repair itself online.