Comment # 5 on bug 1063638 from Antoine Belvire

With the recently added systemd units, btrfs-balance and btrfs-trim cannot run
simultaneously:

~> systemctl cat btrfs-balance
# /usr/lib/systemd/system/btrfs-balance.service
[Unit]
Description=Balance block groups on a btrfs filesystem
Documentation=man:btrfs-balance
After=fstrim.service btrfs-trim.service btrfs-scrub.service

[Service]
Type=oneshot
ExecStart=/usr/share/btrfsmaintenance/btrfs-balance.sh
IOSchedulingClass=idle
CPUSchedulingPolicy=idle
~>

(Thanks to the After= field.)