Though, RAID 1 has the ability to backup one disk to another, you are still under the risk of system crash or virus attack, as well as other disaster, so backing up your operating system is very important, whenever you need to reinstall the operating system, you can restore the system quickly.
RAID 1 - Disk mirroring. Optimized for Redundancy
RAID 1 uses mirroring to write data to multiple drives. This means that when you write a file, the file is actually written to two disks. If one of the disks fails, you can simply replace it and rebuild the mirror.
The tradeoff with RAID 1 is cost. With RAID 1, you must purchase double the amount of storage space that your data requires.
Minimum number of drives: 2
Strengths: high performance; high data protection; minimal penalty on write performance.
Weaknesses: High redundancy cost overhead; because all data is duplicated, twice the storage capacity is required.
Generally, RAID 1 is used to install operating system, whenever one disk failed, you can still use another disk of this RAID. To use RAID 1, you need to connect two disks to the RAID card and construct a RAID 1. After that, the RAID array is detected as a physical hard disk, and then you can install the operating system normally. BTW, this is different with software RAID 1 - Mirrored Volume, to install operating system on Mirrored Volume, you need to install the system on a basic disk firstly, after that convert to dynamic disk in Disk Management, at last add mirror with another free dynamic disk.