There is a lot of choice when it comes to online backup. They are typically great value, but restoring from this sort of backup is slow, potentially even weeks. So remote backups are not terribly helpful if you need to be up and running in a hurry.
The other thing to consider is how long it takes to complete the initial backup. If your connection is slow, it could be weeks or even months before everything is secured. Once that's done, it won't be a big deal to keep future updates secure. But flying without a backup for two weeks is not advised. So online alone isn't enough for full peace of mind.
The fourth backup type: archives
There is another kind of backup: archiving. The idea here isn't so much about immediacy and disaster recovery as being able to access documents you may have worked on a week, a month or a year ago.
As noted in Macworld's Complete guide to Time Machine Apple's Time Machine, built into OS X, can sometimes help regarding previous versions of documents that have been overwritten or accidentally deleted. While we wouldn't recommend using Time Machine instead of a cloning app, it's a good option to use alongside one. Never have multiple backup types going to a single drive, though, because if that hardware fails you lose all of your backups at once.
Beyond Time Machine, there are third-party options for archiving. Get Backup Pro offers archiving as one of four different kinds of backup. Archives can be encrypted, compressed and versioned, depending on your needs, along with being broken down to fit on DVDs. (These days, we'd suggest just archiving to external hard drives, though, given their relatively low cost.)
Keep old Mac data safe, forever, when you upgrade
Another means of creating archives - albeit on an irregular basis - is to swap out your local clone backup whenever making a major upgrade, such as buying a new Mac or upgrading OS X. (In the latter case, note, we're talking about major revisions, such as Yosemite to El Capitan, not minor updates.) Get yourself a new external drive before such big changes, make a last clone of your old computer/OS, and prepare the clone to sit in a cupboard until it's possibly needed again some day.
This might sound unnecessary and expensive, but it's smart for a number of reasons. First, you will now have a bootable backup that has an older OS running on it. If an app stops working or does things differently (for example, audio software not playing instruments in quite the same way as before), you can boot into an old drive and continue work. Secondly, you will have a breakpoint from a certain date with all of your documents on, and can at any point fish out something you accidentally delete from your current Mac. Thirdly, it keeps your current backup drive hardware fresh.
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