I have done a test where I filled up an entire btrfs raid 1 filesystem as a normal user. Then I simulated a failing drive. it turned out I was unable to replace the drive, as raid1 need free space on both drives. See this mail for details [1]
I can understand the technical reasoning behind the requirement of both drives having some free space. But why does btrfs by default allow a normal, non root user to completely fill up the drive? Maybe it's a good idea to reserve some blocks on the filesystem that are only available for the root user, much like ext4 does that (via tune2fs [-m reserved_blocks_percent] and [-r reserved_blocks_count]) [1] https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg92550.html --- Take your mailboxes with you. Free, fast and secure Mail & Cloud: https://www.eclipso.eu - Time to change!
