But if you're not into paying for these services, you can use a free storage called Carbonite. This Carbonite is not the most attractive option for Cloud Backup, but it can do the job of a cloud backup for an even cheaper price than the others. Carbonite doesn't have a premium plan, but costs a measly fee each month
Carbonite's free plan covers one computer; you can get up to five computers with the paid plan, but only one computer can be backed up at a time. While Carbonite offers a lot of options for Cloud Backup, they do have one limitation. Carbonite will back up your files, but not all of them: only those you explicitly set as archived.
That limitation doesn't make much sense, as Cloud Backup are often only a few hundred megabytes in size, and Carbonite can back them up to the cloud. There's no reason to exclude anything, unless you're willing to be selective. If you need to back up all of your files, Carbonite's free plan will do just that.
idrive vs backblaze is a bit more complicated, because it can back up several computers at once. Each computer has its own account, but you can share them between them. You can also set up a network of Cloud Backup using the Carbonite app, which you can download for free from the Carbonite website. (If you want to use a computer across a wired network, you can use a USB key, but Carbonite doesn't provide that option.) This way, you can back up multiple computers to the same account, but you can't specify which ones.
The main drawback of Carbonite is that in order to back up your files, you'll have to pay for them. You can back up only one computer at a time, and you're only charged for the ones you select. This is less than ideal. While there's no way to specify which files you want to back up, you can specify that you want to back up all your files (which Carbonite does) or none of them (Carbonite does).