Understanding RAID level-x0

Note: RAID level-x0 is not available on all controllers.

RAID level-x0 refers to RAID level-10 and RAID level-50. RAID level-x0 is a multi-level disk group, or a spanned disk group. The operating system uses the spanned disk group logical device in the same way as a regular disk group logical device.

RAID level-x0 allows more physical drives in a disk group. The benefits of doing so are larger logical devices, increased performance, and increased reliability. For example, RAID level-5 cannot use more than 16 physical drives in an disk group; however, RAID level-10 and 50 support 48 drives.

RAID level-x0 requires a minimum of two drives and supports a maximum of 48 drives.

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

RAID level-10 example

Start with six physical drives.
Create three disk groups (labeled A, B, and C), each disk group using two physical drives.
Then create a spanned disk group (labeled as *) that spans the three disk groups.
A sub-logical device is created within each disk group (A, B, and C). Then the data is striped across the physical drives in the disk group, creating blocks.

Notice that, in each disk group, the data on the drive on the right is a copy of the data on 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 device within the spanned disk group (*).

The data is striped across this logical device, creating blocks (1-12). Notice that none of these blocks are redundant. This is because the logical drive is RAID level-0 in a RAID level-x0 implementation (see the following table).

 

RAID level Sub-logical device Spanned disk group logical device
10 RAID level-1 RAID level-0
50 RAID level-5 RAID level-0

With RAID level-10 and 50, if one of the physical drives fails in a sub-logical drive, the controller switches read and write requests to the remaining functional drives in the sub-logical device.

RAID level-x0 offers the following advantages and disadvantages.

Advantages Disadvantages
  • Supports up to 48 physical drives
  • 100% data redundancy

  • Not available on all controllers

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