## Understanding RAID level-1

RAID level-1 provides 100% data redundancy and requires only two physical drives. With RAID level-1, the first half of a stripe is the original data; the second half of a stripe is a mirror (that is, a copy) of the data, but written to the other drive in the RAID level-1 array.

Because the data is mirrored, the capacity of the logical drive when assigned RAID level-1 is 50% of the array capacity.

The following illustration shows an example of a RAID level-1 logical drive.

### RAID level-1 example

Start with two physical drives. |
Create an array using the two physical drives. |
Then, create a logical drive within that array. |
The data is striped across the drives, creating blocks. Notice that the data on the drive on the right is a copy of the drive on the left. |

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

See also

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