CentOS - May 2017 - External drive, BackupPC service, and booting

I'm using an external drive with BackupPC on CentOS 7. I currently have a 
mount entry like this in fstab:

/dev/disk/by-label/backuppc4              /var/lib/BackupPC       ext4 
noauto,rw       0 0

This means I must manually mount the drive and then start the backuppc 
service.

Is there a way to set up hotplugging so that the drive is mounted if 
present at boot time but doesn't stop the boot if it's not present or 
otherwise fails? I see the fstab nofail option. Will that do what I want?

Is there a way to set up the backuppc service (through systemd) so that it 
starts if and only if the drive is present, or starts if the drive is 
plugged in later?

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