COVER: Alleviating Crash-Consistency Error Amplification in Secure Persistent Memory Systems

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Data security (including confidentiality, integrity, and availability) and crash consistency guarantees are essential for building trusted persistent memory (PM) systems. Security and consistency metadata are added to enable the guarantees. Recent studies show that errors in security metadata have the amplified effect, which significantly affects data availability. However, the impact of consistency metadata errors on data availability has rarely been discussed. We identify the crash-consistency error amplification (CCEA) problem, several errors in consistency metadata can make a large portion of data in PM possibly inconsistent. The error sensitivity of consistency metadata is higher than data and security metadata, thus requiring special attention. It is inefficient to address this problem by using the methods that are proposed to alleviate the amplified effect of security metadata errors, because security metadata are generally designed for a single purpose (e.g., integrity verification), while consistency metadata are designed for multiple purposes, including inconsistency locating and recovery. To effectively and efficiently alleviate the CCEA problem, we propose a c rash c o nsistency ver ification approach (COVER) that decouples inconsistency locating and recovery. COVER provides three design options that support different tradeoffs between effectiveness and efficiency. Experimental results show that COVER effectively alleviates the problem with only about 1.0% performance degradation on average compared with the state-of-the-art secure PM design.