In this question I asked what how to not make a media failure halt the system boot process. However, I got two suggestions for fstab options
What is the difference between the two?
This is what
As mentioned by Stéphane, nobootwait is limited to ubuntu+derivatives.
Nofail will keep trying to mount the drive as cjm pointed out, however, the boot process will continue after the mount reaches timeout. If you don't expect the drive to be there regularly as to warrant the extra 90 seconds or so bootup when it's absent, don't automount it in fstab.
(P.S. I put this as cjm's answer sounds as if the system will ultimately fail to boot. It would have been a comment but I don't have the reputation yet).