The fastest way to get back to work after the worst has happened is to have a local backup, one that you can boot from ideally. If you have a local HDD with a complete copy of your boot drive, then restarting with the alt key applied will give the option of starting from the external drive. You could be up and running again in five minutes, which can be a lifesaver if your job depends on it.
There aren't too many downsides to a local backup. They won't help if there is a fire. Only an offsite, or online backup can help there. But otherwise a daily backup to a local drive will be sufficient for most. Although that still leaves the potential for the loss of a day's work.
To make sure you don't lose anything at all, the third strand of my backup strategy is live backup. DropBox is the leader here, but here are alternatives. Live backup means that as soon as you save your file, a copy is made in your backup. This is amazing, but not practical for whole drives because of the way the software is designed. But if you keep everything you might keep in your Documents Folder, in your DropBox folder, you will secure your most irreplaceable documents.
Protecting from drive failure, losing a drive, or accidentally deleted files
There are two main reasons for backups. Either data is gone due to a failure or loss of a drive, or data is accidentally deleted. Deleted data may mean you want to go back in time, to a point before you deleted it. This means keeping lots of backups, or partial backups. A full backup may take up a lot of space, so keeping a week's worth of full backups is usually unrealistic. Instead a full backup is then updated with incremental or versioned backups. So if you know you had a file a week ago, you can go to a backup from that time to retrieve it.
So that's the three-pronged approach to backup I would recommend.
Local backup, for fast recovery
Live backup, for your most precious files as you create them
Online backup, to secure large amounts of data, but slowly
Additionally, I would recommend the local backup be a bootable drive to minimize downtime. It's also handy to have at least one of the backups be versioned, or incremental, so that you can retrace your steps to find deleted files.
Local bootable disk backup
Local backups are fastest, but there's the expense of a backup hard drive to consider too. However if you haven't bought an external HDD lately, you're in for a pleasant surprise. Prices have tumbled over the last few years, and capacities have soared.
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