[CentOS] mount options

Hi all!

I've got a Venus DS3R Pro2 external drive unit with two drives set up as RAID-1, and the raid volume is formatted as ext4.

it is listed in /etc/fstab as:

UUID=f787c482-fb92-4ba7-87d6-cfeaef6b64c2 /mnt/backup ext4 defaults,users 0 2

if the external unit (which attaches via e-sata) is NOT powered on when the system boots, it hangs and drops to a maintenance prompt.

I'd sure like to have it defer that particular mount and continue to boot.

I've been perusing various mount man pages, but don't see any ext4 (or non-filesystem-specific) opotions to allow this.

Can any of you offer helpful advice in this matter?

Thanks!

Fred