A RAID 5 configuration with 20 hard drives loses one hard drive. How many additional hard drive failures can this configuration tolerate before data loss?

In a RAID 5 configuration, data is distributed across multiple hard drives with parity information used for redundancy. This parity allows the RAID array to recover from the failure of one hard drive without data loss. When one hard drive fails, the RAID array can continue to function normally, relying on the parity data to reconstruct any lost information.

However, RAID 5 can only tolerate a single hard drive failure at a time. If a second hard drive fails while the first one is still offline, there will not be enough data or parity available to reconstruct the data of the failed drives. As a result, the configuration would be unable to recover, leading to data loss.

Therefore, in the scenario where there are 20 hard drives in a RAID 5 configuration that has already lost one drive, it can tolerate no additional hard drive failures before data is compromised. This means that the correct interpretation is that the system can withstand 0 additional failures after losing one drive.