Understanding RAID level-5

RAID level-5 stripes data and parity across all drives in the array.

RAID level-5 offers both data protection and increased throughput. When you assign RAID level-5 to an array, the capacity of the array is reduced by the capacity of one drive (for data-parity storage). RAID level-5 gives you higher capacity than RAID level-1, but RAID level-1 offers better performance.

RAID level-5 requires a minimum of three drives and, depending upon the level of firmware and the stripe-unit size, supports a maximum of 8 or 16 drives.

The following illustration is an example of a RAID level-5 logical drive.

RAID level-5 example

Start with four physical drives.
Create an array using three of the physical drives, leaving the fourth as a hot-spare drive.
Then create a logical drive within that array.
The data is striped across the drives, creating blocks.

Notice that the storage of the data parity (denoted by *) also is striped, and it shifts from drive to drive.

A parity block (*) contains a representation of the data from the other blocks in the same stripe. For example, the parity block in the first stripe contains data representation of blocks 1 and 2.

If a physical drive fails in the array, the data from the failed physical drive is reconstructed onto the hot-spare drive.

RAID level-5 offers the following advantages and disadvantages.
Advantages Disadvantages
  • 100% data protection
  • Offers more physical drive storage capacity than RAID level-1 or level-1E

Lower performance than RAID level-1 and level-1E

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