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 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

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