I thought a lot on this subject and I realized that Microsoft OneDrive is not for backup your data. It is more like a online sync storage which you can access from any device including PC, tablet and phone (including Windows Phone, iPhone, Android Phone, iPad).
Backup is like, if you accidentally delete some data you can restore them from backup or you can restore data to some previous state. OneDrive remains in sync with your PC so that if you accidentally delete some data it will also delete it from OneDrive and you cannot restore them. It is not a traditional backup system.
The main objective behind OneDrive is you can store your data online which you can access from any device. Your data remains in sync with OneDrive cloud storage and your PC. For example I want to access my pictures from PC as well as my phone and I am storing them on my OneDrive.
Please remember you should backup all your important data including which you store in cloud like OneDrive, GoogleDrive etc. You can backup your data offline in an external hard disk with Windows Backup and Restore or you can backup online with cloud solution with something like CrashPlan.
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