Enter me, wanting to replace one of the disks. You might already be seeing where this story is going. So there's sda1 & sdb1. I proceeded running btrfs replace $sdb1 $sdc1 $mntpoint. After it succeeded, the array suddenly got unmounted. The reason was probably that the now UUID-less sdb1 was the one mounted "on paper" and after it was replaced the UUID no longer pointed to it.
So... I love btrfs but first impressions of doing RAID 1 with btrfs haven't been too positive. After you add a second disk to a filesystem, the only useful identifier the whole filesystem has appears to be its UUID — which is the exact same on both partitions of the array. And when the array gets mounted, as far as the system is concerned, "on paper" only one of the disks is mounted. Which one? The one that was lucky to get assigned /dev/disk/by-uuid/$UUID.
Enter me, wanting to replace one of the disks. You might already be seeing where this story is going. So there's sda1 & sdb1. I proceeded running btrfs replace $sdb1 $sdc1 $mntpoint. After it succeeded, the array suddenly got unmounted. The reason was probably that the now UUID-less sdb1 was the one mounted "on paper" and after it was replaced the UUID no longer pointed to it.
Enter me, wanting to replace one of the disks. You might already be seeing where this story is going. So there's sda1 & sdb1. I proceeded running btrfs replace $sdb1 $sdc1 $mntpoint. After it succeeded, the array suddenly got unmounted. The reason was probably that the now UUID-less sdb1 was the one mounted "on paper" and after it was replaced the UUID no longer pointed to it.
