page_title: Non-standard RAID levels
section_title: Double parity
hierarchical_section_title: Non-standard RAID levels / Double parity
context_page_description: Although all RAID implementations differ from the specification to some extent, some companies and open-source projects have developed non-standard RAID implementations that differ substantially from the standard. Additionally, there are non-RAID drive architectures, providing configurations of multiple hard drives not referred to by RAID acronyms.
context_section_description: Now part of RAID 6, double parity (sometimes known as row diagonal parity) features two sets of parity checks, like traditional RAID 6. Differently, the second set is not another set of points in the over-defined polynomial which characterizes the data. Rather, double parity calculates the extra parity against a different group of blocks. For example, in our graph both RAID 5 and 6 consider all A-labeled blocks to produce one or more parity blocks. However, it is fairly easy to calculate parity against multiple groups of blocks, one can calculate all A blocks and a permuted group of blocks.
caption: Diagram of a RAID-DP (double parity) setup
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