Most common in desktops, workstations and (mandatory in) servers than in regular laptops, hard drives and storage units are mirrored -or in a similar arrangement- so that if one of them is damaged, the other(s) make(s) the whole system operate normally; the idea is to replace the broken unit as soon as possible so that redundancy is attained again.
There are many ways to achieve redundancy in the internal storage units on servers and networked storage devices. The main point here is to make sure that hardware does not become an issue for keeping our data safe. Power outages and current spikes, heat, regular wear and such could cause such damage.
Obviously, the better the storage units’ quality, number of them, and array type will secure data better.