TVARAK: Software-Managed Hardware Offload for Redundancy in Direct-Access NVM Storage

Production storage systems complement device-level ECC (which covers media errors) with system-checksums and cross-device parity. This system-level redundancy enables systems to detect and recover from data corruption due to device firmware bugs (e.g., reading data from the wrong physical location). Direct access to NVM penalizes software-only implementations of system-level redundancy, forcing a choice between lack of data protection or significant performance penalties. We propose to offload the update and verification of system-level redundancy to TVARAK, a new hardware controller co-located with the last-level cache. TVARAK enables efficient protection of data from such bugs in memory controller and NVM DIMM firmware. Simulation-based evaluation with seven data-intensive applications shows that TVARAK is efficient. For example, TVARAK reduces Redis set-only performance by only 3%, compared to 50% reduction for a state-of-the-art software-only approach.