I had RAID 1 with 2 hard drives and never even bothered to backup my files. As I never expected that it would happen, a virus wiped all the data on both of my hard drives. This experience has changed my entire view on backups I used to think they were unneeded for RAID 1, its sad that it takes such a disastrous event like this to open my eyes.
Since RAID 1 is mirrored, you can disconnect one of the drives from the array and connect it as slave to a healthy system and install any Data Recovery Software depending on the file system of the drive. But be careful that you don’t change the order of the drives while reconnecting it back to the array.
If you fail recovering the data using the software then you can send your RAID drives to a professional Data Recovery Labs who offer RAID Recovery services and are well experienced in this field.