Which of the following describes a "double fault" condition in a RAID array?

A "double fault" condition in a RAID array refers to a situation where multiple drives experience errors and fail simultaneously. This can lead to a critical failure of the RAID array and data loss, especially in configurations where redundancy relies on having at least one working drive to maintain data integrity.

In RAID configurations, the risk of simultaneous drive failures is a significant concern, particularly in arrays that do not have enough redundancy to withstand such an event. For example, in RAID levels that use striping without mirroring, the failure of more than one drive can result in the complete loss of all data stored in that array.

The other options do not accurately describe a "double fault." A single drive failure refers to just one drive having issues, which does not encapsulate the concept of multiple failures. When all drives are operating normally, this is the ideal state for a RAID array, and it does not reflect any fault condition. Similarly, if only the last drive in the array is functional, it implies that other drives have failed, but it does not necessarily denote multiple drives failing at the same time, which is essential for defining a "double fault."