Impact of disk corruption on open-source DBMS

Despite the best intentions of disk and RAID manufacturers, on-disk data can still become corrupted. In this paper, we examine the effects of corruption on database management systems. Through injecting faults into the MySQL DBMS, we find that in certain cases, corruption can greatly harm the system, leading to untimely crashes, data loss, or even incorrect results. Overall, of 145 injected faults, 110 lead to serious problems. More detailed observations point us to three deficiencies: MySQL does not have the capability to detect some corruptions due to lack of redundant information, does not isolate corrupted data from valid data, and has inconsistent reactions to similar corruption scenarios. To detect and repair corruption, a DBMS is typically equipped with an offline checker. Unfortunately, the MySQL offline checker is not comprehensive in the checks it performs, misdiagnosing many corruption scenarios and missing others. Sometimes the checker itself crashes; more ominously, its incorrect checking can lead to incorrect repairs. Overall, we find that the checker does not behave correctly in 18 of 145 injected corruptions, and thus can leave the DBMS vulnerable to the problems described above.