Understanding RAID level-1 Enhanced

If you have three or more hard disk drives in the array, you can no longer select RAID level-1, but you can select RAID level-1 Enhanced (also called RAID 1E).

The RAID level-1 Enhanced combines mirroring with data striping. This RAID level stripes data and copies of the data across all 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 of the grouping of hard disk drives in the array.

RAID level-1 Enhanced requires a minimum of three drives and, depending on the stripe-unit size, supports a maximum of eight or 16 drives.

RAID level-1 Enhanced example

You have three physical drives.
Create an array with the physical drives.
Then, create a logical drive within the 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 mirror (that is, the copy) of the preceding data stripe. Also notice that each block on the mirror stripe is shifted one drive.

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

See also

Selecting a RAID level
RAID level-0
RAID level-1
RAID level-5
RAID level-5 Enhanced