A raid 1 array just clones the data to another drive so they both have the same data, a raid 5 array needs at least 3 drives but with this array one can loose one drive and the data will still be safe but typically you cannot expand the array to have more disk and when setting up an array the disk typical need to be the same size and spindle speed if using a standard hard drive this link seems to have good information on how raid array work I only skimmed through it though. https://www.microsemi.com/product-directory/raid-controllers/4047-raid-levels#:~:text=As the most common and,all drives (Figure 5).

It is either the port or the charging cable