# Understanding RAID level-1 Enhanced

RAID level-1 Enhanced (RAID level-1E) combines mirroring and 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% of the array capacity.

RAID level-1E has a similar profile to RAID level-1; it provides data redundancy and high levels of performance, but the storage capacity is diminished. However, RAID level-1E allows a larger number of physical drives to be used.

RAID level-1E 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-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.

RAID level-1E offers the following advantages and disadvantages:

Advantages | Disadvantages
--- | ---
100% data redundancy High performance | Allows only 50% of the physical drive storage capacity to be used

## More information

- 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

Glossary | Contents

x-1047-SRM-00-03-EN