Erasure coding protects data by splitting it into a defined number of data segments and calculating a separate set of coding (parity) segments, then distributing all of these segments across different physical drives; the mathematical property of this scheme is that the original data can be fully reconstructed as long as any subset of segments equal to the number of data segments survives, meaning the array can tolerate losing exactly as many segments (drive failures) as there are coding segments before data becomes unrecoverable. In this configuration, described as 10 data segments plus 4 coding segments (commonly notated as a 10+4 scheme), the number of coding segments is 4, which directly determines the maximum number of simultaneous drive failures the configuration can withstand while still allowing full data reconstruction: exactly 4. If a fifth drive were to fail simultaneously, the number of surviving segments would drop below the 10 needed to reconstruct the original data, resulting in data loss. This is directly analogous to how RAID parity works, but generalized so that erasure coding schemes can be tuned with a larger number of coding segments than traditional RAID levels typically support, allowing for much higher fault tolerance in large-scale distributed storage systems. The correct answer, 4, matches the number of coding segments configured.

Reference topic: Fault Tolerance Techniques - Erasure Coding Fault Tolerance Calculation.