backup
noun [ C or U ]
(also back-up) uk/ˈbækʌp/ usa person, plan, piece of equipment, etc. that you can use to replace another if necessary:
I use my other email account as a backup.
The company is exploring alternative sources to provide backup for materials when the suppliers cannot deliver.
Remember that your colleagues are your backup system when things go wrong.
IT
an extra copy of the information on a computer, that is stored separately:
Keep a backup of your data in case a drive fails.