Beyond RAID 6 --- an Efficient Systematic Code Protecting Against Multiple Errors, Erasures, and Silent Data Corruption
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We describe a replacement for RAID 6, based on a new linear, systematic code, which detects and corrects any combination of E errors (unknown location) and Z erasures (known location) provided that Z+2E ≤ 4. We investigate some scenarios for error correction beyond the code's minimum distance, using list decoding. We describe a decoding algorithm with quasi-logarithmic time complexity, when parallel processing is used: ≈ O( N) where N is the number of disks in the array (similar to RAID 6). By comparison, the error correcting code implemented by RAID 6 allows error detection and correction only when (E,Z)=(1,0), (0,1), or (0,2). Hence, when in degraded mode (i.e when Z ≥ 1), RAID 6 loses its ability for detecting and correcting random errors (i.e E=0, which is known as a silent data corruption). In contrast, the proposed code does not experience silent data corruption unless Z ≥ 3. These properties, the relative simplicity of implementation, vastly improvement data protection, and low computational complexity of the decoding algorithm, make this code a natural successor to RAID 6. As our proposed code is based on the use of quintuple parity, then this justifies our proposal to call it PentaRAID.
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