Which of the following can help prevent data loss on a RAID array in the event of a power failure?

Using a RAID mirror provides redundancy against drive failure but does not inherently protect data held in a volatile write cache from being lost during an unexpected power loss before it is committed to disk.

A battery backed write cache holds pending write operations in volatile memory within the RAID controller. In the event of a sudden power failure, the battery provides temporary power, allowing these pending writes to be flushed to disk or preserved until power is restored, thereby preventing data loss.

Using RAID with parity provides fault tolerance against drive failure and allows data reconstruction, but it does not specifically protect data held in a volatile write cache from being lost during a power outage before it's written to disk.

A battery backed read cache primarily stores frequently accessed data to improve read performance and does not play a role in protecting unsaved write data from loss during a power failure.