A storage system storing logical volume data in a redundant array of independent disks (RAID) 6 configuration stripes the volume data across corresponding physical regions on two or more data storage devices, and stores two parity values to corresponding physical regions on two parity storage devices. As a result of mathematical calculations (e.g., Reed Solomon encoding calculations), storage devices arranged in a RAID 6 configuration have an ability to recover from a failure of any two of the storage devices.
An additional feature of RAID 6 is an ability, while processing a write operation, to recalculate the two parity values without retrieving all the corresponding physical regions on the data storage devices. For example, while processing a request to write new data to a given one of the storage devices, the two parity values can be calculated using the new data, existing data currently stored on given one of the storage device that is to be replaced with the new data, and two existing current parity values currently stored on the parity storage devices. Therefore, to process a request to write data to a given data storage device in a RAID 6 8+2 configuration, the two parity values can be calculated with data obtained via three read operations.
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The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.