## Understanding RAID level-x0

RAID level-x0 refers to RAID levels-00, 10, 1E0, and 50. RAID level-x0 includes more physical drives in an array. The benefits of doing so are larger logical drives, increased performance, and increased reliability. RAID levels-0, 1, 1E, 5, and 5E cannot use more than 16 physical drives in an array. However, RAID levels-00, 10, 1E0, and 50 include more physical drives by managing an array of arrays, or a spanned array. The operating system uses the spanned array logical drive the same as a regular array logical drive.

Note: RAID level-x0 is only available on the IBM ServeRAID-4H Ultra160 SCSI controller.

RAID level-x0 requires a minimum of 2 drives and supports a maximum of 60 drives.

The following illustration is an example of a RAID level-10 logical drive.

### RAID level-10 example

Start with six physical drives. |
Create three arrays (labeled A, B, and C), each array using two physical drives. |
Then, create a spanned array (labeled as 1) that spans the three arrays. |
A sub-logical drive is created within each array (A, B, and C). Then, the data is striped across the physical drives in the array, creating blocks. Notice that, in each array, the data on the drive on the right is a copy of the drive on the left. This is because the sub-logical drives (A, B, and C) are RAID level-1 in a RAID level-10 implementation (see the following table). |
Then, create a logical drive within the spanned array (1). The data is striped across this logical drive, creating blocks. Notice that none of these blocks are redundant. This is because the logical drive (1) is RAID level-0 in a RAID level-x0 implementation (see the following table). |

RAID level | means the sub-logical drive is | and the spanned array logical drive is
--- | --- | ---
00 | RAID level-0 | RAID level-0
10 | RAID level-1 | RAID level-0
1E0 | RAID level-1E | RAID level-0
50 | RAID level-5 | RAID level-0

With RAID level-10, 1E0, and 50, if one of the physical drives fails in a sub-logical drive, the ServeRAID controller switches read and write requests to the remaining functional drives in the sub-logical drive. With RAID level-00, a physical drive failure within the sub-logical drive results in loss of data.

See also

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