I know how RAID work and prevent data lost from disks failures. I want to know is possible way/how easy to recover data from unfunctioned remaining RAID disks due to RAID controller failure or whole system failure. Can I even simply attach one of the RAID 1 disk to the desktop system and read as simple as USB disk? I know getting data from the other RAID types won’t be that simple but is there a way without building the whole RAID system again. Thanks.
This is poorly phrased. A raid with a bad disk is not failed, it is degraded. The entire array is not more likely to fail than a single disk.
Yes, you are more likely to experience a disk failure, but like you said, only because you have more disks in the first place. (However, there is also the phenomenon where, after replacing a failed disk, the additional load during the rebuild might cause a second disk to fail, which is why you should replace failed disks as soon as possible. And have backups.)