The general reccomendation is a 3-2-1 Backup strategy, meaning you have 3 copies: 2 local, 1 offsite. Here's one way:

• Get a NAS appliance (like a Drobo) to protect against a single disk crash
  • (or just an external disk, with no single disk failure protection)
• Add an Apple Time Machine to get your 2nd local copy.
  • If Time Machine is not for you, get another external drive and some other software (Crashplan can do this) to make a local backup.
  • The point of this 2nd copy is (1) quicker restore, (2) immediate backups while the cloud catches up, (3) do you trust your cloud backup service completely?
• Use some service like CrashPlan, BackBlaze, Amazon Prime, ... to do offsite backups.
  • This protects you from fire, theft, flood, lightning, ...

The downside to these off-the-shelf solutions is they do not protect against bit rot on the disks. To get that, best I can tell, you'll need to do something custom like periodically running par2 or deploying a custom FreeNAS appliance with ZFS.

Also keep in mind that a mirror is not a good backup -- if you mirror new files and also sync the deletion of files, you'll have the ability to recover from a disk disaster (assuming your disaster wasn't the kind that made files look like they were removed!), but your recovery path from user error (oops, I deleted something I shouldn't have!) is very limited.

You also want to retain file history (not just the latest copy!) to protect yourself from crypto trojans. Most cloud services do this. Your 2nd local copy should do this as well.

For moving the photos, I would copy them using rsync. The benefit of rsync is if it is interrupted, it can be restarted and will skip files already copied.