## Understanding RAID level-1 Enhanced

If you have three or more physical drives in the array, you cannot select RAID level-1; you can select RAID level-1 Enhanced (RAID level-1E).

RAID level-1E combines mirroring with data striping. This RAID level stripes data and copies of the data across all of the drives in the array. As with the standard RAID level-1, the data is mirrored, and the capacity of the logical drive is 50 percent of the array capacity of the grouping of physical drives in the array.

RAID level-1E requires a minimum of 3 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-1E logical drive.

### RAID level-1 Enhanced example

Start with three physical drives. |
Create an array using the physical drives. |
Then, create a logical drive within that array. |
The data is striped across the drives, creating blocks. Notice that the stripe labeled *is the data stripe and the stripe labeled ** is the copy of the preceding data stripe. Also notice that each block on the mirror stripe is shifted one drive. |

With RAID level-1E, if one of the physical drives fails, the ServeRAID controller switches read and write requests to the remaining functional drives in the RAID level-1E array.

See also

Understanding RAID technology
Understanding stripe-unit size
Selecting a RAID level
RAID level-0
RAID level-1
RAID level-5
RAID level-5 Enhanced
RAID level-x0