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Xserve RAID Solutions Linux RAID Solutions
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RAID 6 Level Explanation and Solutions |
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RAID level 6 is similar to RAID level 5 but with two sets of parity information instead of one. RAID 6 level stripes blocks of data and parity across all drives in the array like RAID 5, but adds a second set of parity information for each block of data. When you assign RAID 6 level to an array, the capacity of the array is reduced for data-parity storage (the exact amount depends on the size of the drives in the array). The second set of parity information is added to improve fault tolerance. RAID level 6 can handle two simultaneous drive failures, where other single RAID levels can handle, at most, only one. RAID 6 level requires a minimum of four drives and supports a maximum of 16 drives. The maximum stripe-unit size depends on the number of drives in the array. The following illustration is an example of a RAID 6 logical drive. Start with six physical drives. Create a logical drive using four physical drives, leaving two for hot spare drives. The data is striped across the drives, creating blocks in the logical drive. The storage of the data parity (denoted by * and **) is striped, and it shifts from drive to drive as it does in RAID level-5. If a physical drive fails in the array, the logical drive is degraded but remains fault tolerant. If a second physical drive fails in the array, the data from the failed drives are reconstructed onto the hot-spare drives, and the data for the logical drive return to the original striping scheme. RAID level 6 offers the following advantages and disadvantages. * 100% data protection
* Lower performance than RAID level-5 because of two parity drives |
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