Am 20.04.2016 um 15:32 schrieb Anand Jain: >> 1. mount the raid1 (2 disc with different size) > >> 2. unplug the biggest drive (hotplug) > > Btrfs won't know that you have plugged-out a disk. > Though it experiences IO failures, it won't close the bdev. Well, as far as I can tell mdadm can handle this use case. I tested that. I have an mdadm raid5 running. I accidentially unplugged a sata cable from one of the devices and the raid still worked. I did not even notice that the cable was unplugged until a few hours later. Then I plugged in the cable agaib and that was it. mdadm recovered the raid5 without any problem. -> This is redunancy! > >> 3. try to copy something to the degraded raid1 > > This will work as long as you do _not_ run unmount/mount. I did not umount the raid1 when I tried to copy something. As you can see from the sequence of events: I removed the drive and immdiately afterwards tried to copy something to the degraded array. This copy failed with a crash of the btrfs module. -> This is NOT redundancy. The ummount and mount operations are coming afterwards. In a nutshell I have to say that the btrfs behaviour is by no means compliant with my understanding of redundancy. Matthias -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
