Exam NCA topic 1 question 30 discussion

Refer to the exhibit.

After an abrupt power outage, an administrator receives a number of alerts indicating disks are failed. Prism Element shows a large number of disks offline as seen in the diagram. This single block, four node cluster is configured FT1 with an RF2 container holding all user data.
What number of drive failures on different domains (node, block, or rack) could this configuration have tolerated prior to seeing data unavailability?