Using replace is the preferred solution, and 2-3x faster than balance. (device remove first rebalances.)

This answer prevents the failed disk from blocking kernel I/O.

I did the following:

1. Ensured that the degraded filesystem was noauto in /etc/fstab

2. Rebooted the machine (which took about 20 minutes due to I/O hangs)

3. Disabled the LVM VG containing the btrfs fs on the failed drive:

    sudo vgchange -an <failed-vg> 

4. Disabled the failed device:

    echo 1 | sudo tee /sys/block/sdb/device/delete 

5. Mounted the filesystem -o rw,degraded (Note: degraded can only be used once)

6. Got the failed devid from:

    btrfs filesystem show /mountpoint 

7.  btrfs replace start -B <devid> /dev/new-disk /mountpoint 

As I'm writing this:

• replace status shows a healthy 0.1% progress every 30 seconds or so
• iostat -d 1 -m <target-dev> shows about 145MB/s (Seagate advertises 160MB/s)

Using replace is the preferred solution, and 2-3x faster than balance. (device remove first rebalances. Perhaps it doesn't use the soft conversion type making it slower)

This answer prevents the failed disk from blocking kernel I/O.

I did the following:

1. Ensured that the degraded filesystem was noauto in /etc/fstab

2. Rebooted the machine (which took about 20 minutes due to I/O hangs)

3. Disabled the LVM VG containing the btrfs fs on the failed drive:

    sudo vgchange -an <failed-vg> 

4. Disabled the failed device:

    echo 1 | sudo tee /sys/block/sdb/device/delete 

5. Mounted the filesystem -o rw,degraded (Note: degraded can only be used once)

6. Got the failed devid from:

    btrfs filesystem show /mountpoint 

7.  btrfs replace start -B <devid> /dev/new-disk /mountpoint 

As I'm writing this:

• replace status shows a healthy 0.1% progress every 30 seconds or so
• iostat -d 1 -m <target-dev> shows about 145MB/s (Seagate advertises 160MB/s)