Also you have to remember to back your stuff on on the external drive on some sort of set schedule. Services like Carbonite are “set it and forget it”.
All operating systems have some kind of schedule service. You can create a backup and schedule it to run at a particular time, daily, weekly, or whatever. I use Windows Xcopy to copy my files to a second internal SATA drive, using the option to copy only files whose date on the target drive is earlier than that on the source (this prevents having to copy every file every time). I put the commands in a batch file and use the Schedule service to run it every morning. For extra security I archive my data onto DVD media about once every six months and keep the media at a remote location.
Most backup drives use a software that discreetly synchronizes in the background.
Services like Carbonite are set it and forget it.
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So are other programs that you can put on your computer to back up to external hard drives.