Understanding RAID level-x0

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

RAID level-x0 refers to RAID level-10, RAID level-50, and RAID level-60. RAID level-x0 is a multi-level pool, or a spanned pool. The operating system uses the spanned pool logical device in the same way as a regular pool logical device.

RAID level-x0 allows more physical drives in a pool. 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 pool; however, RAID 50 supports 60 drives.

RAID level-x0 requires a minimum of two drives and supports a maximum of 128 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 pools (labeled A, B, and C), each pool using two physical drives.
Then create a spanned pool (labeled as *) that spans the three pools.
A sub-logical device is created within each pool (A, B, and C). Then the data is striped across the physical drives in the pool, creating blocks.

Notice that, in each pool, 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 pool (*).

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 pool logical device
10 RAID level-1 RAID level-0
50 RAID level-5 RAID level-0
60 RAID level-6 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. With RAID level-60, if one or two 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 128 physical drives
  • 100% data redundancy

  • Not available on all controllers

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