btrfs crashed system last output from watch cmd:

gistfile1.txt

Data, single: total=640.00GiB, used=628.88GiB
Data, RAID5: total=786.00GiB, used=785.99GiB
System, RAID1: total=64.00MiB, used=196.00KiB
Metadata, RAID1: total=269.00GiB, used=2.29GiB
unknown, single: total=512.00MiB, used=0.00   

Label: 'massive'  uuid: b705fef7-a604-4ba1-bc43-bc387e58c733
        Total devices 3 FS bytes used 1.38TiB
        devid    1 size 1.77TiB used 1.01TiB path /dev/sdb2
        devid    2 size 875.63GiB used 662.06GiB path /dev/sdc2
        devid    3 size 875.63GiB used 662.06GiB path /dev/sdd2

Btrfs v3.14.2-dirty

Balance on '/mnt/massive' is running
159 out of about 552 chunks balanced (269 considered),  71% left