Home About Igor Ostrovsky Blogging On programming, technology, and random things of interest Algorithms Cool Stuff C# RoboZZle Concurrency Misc Sep 29 How RAID-6 dual parity calculation works Parity protection is a common technique for reliable data storage on mediums that may fail (HDDs, SSDs, storage servers, etc.) Calculation of parity uses tools from algebra in very interesting ways, in particular in the dual parity case. This article is for computer engineers who would like to have a high-level understanding of how the dual parity calculation works, without diving into all of the mathematical details. Let’s start with the simple case – single parity. As an example, say that you need to reliably store 5 data blocks of a fixed size (e.g., 4kB). You can put the 5 data blocks on 5 different storage devices, and then store a parity block on a 6t...