RAID level-6 is similar to RAID level-5 but with two sets of parity information instead of one. RAID level-6 stripes blocks of data and parity across all drives in the pool like RAID level-5, but adds a second set of parity information for each block of data.
When you assign RAID level-6 to a pool, the capacity of the pool is reduced for data-parity storage (the exact amount depends on the size of the drives in the pool). 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 level-6 requires a minimum of four drives and supports a maximum of 16 drives. The maximum stripe size depends on the number of drives in the pool.
The following illustration is an example of a RAID level-6 logical device.
Start with six physical drives. | ![]() |
Create a logical device using four physical
drives, leaving two for hot spare drives.
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The data is striped across the drives, creating blocks in the logical device. 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 pool, the logical device is degraded but remains fault tolerant. | ![]() |
If a second physical drive fails in the pool, the data from the failed drives are reconstructed onto the hot-spare drives, and the data for the logical device return to the original striping scheme. |
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RAID level-6 offers the following advantages and disadvantages.
Advantages | Disadvantages |
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