Kurt's point is solid in that you want redundancy of backups when it comes to something as important as photos.
But....here's something to think about.
A good number of people will use online backup and never really verify that all of their photos exist in the cloud. If you have a lot of photos, make sure they are all backed up to your online storage. Here is where some human methodology can help.
If you have a good number of photos within a folder, make one subfolder for every 50 or 100 photos. Put exactly 50, 75, or 100 photos in a subfolder. Then, as you backup to the cloud (or even a connected hard drive for that matter), you can quickly see if a sub folder has been completely backed up. I know this sounds like overkill but all it takes is missing that one special photo that is irreplaceable .....
...just don't forget about that online account. Check on it - log into the account one per quarter (place a reminder on your calendar) so it does NOT become inactive and/or deleted.