Multi-level RAID 0+1 combines the performance enhancements of RAID 0 with the redundancy of RAID 1. A RAID 0+1 array is constructed by taking a RAID 0 array consisting of two or more disks and mirroring the entire array to a different array consisting of an equal number of disks. This creates a RAID 1 Super-Array consisting of two RAID 0 Sub-Arrays. RAID 0+1 is often referred to as a mirror of stripes because it operates by creating a mirror of a stripe set. Some people might refer to this configuration as a RAID 1+0 but this does not follow most industry standards. The standard multi-level RAID naming convention is to list the Sub-Array first and the Super-Array second. The following chart illustrates a RAID 0+1 setup for an array of six disks. To see the difference between RAID 0+1 and RAID 1+0,
see our RAID 1+0 page.
RAID 0 (stripes)
| RAID 1 Super-Array (mirror) |
Disk 1 |
Disk 2 |
Disk 3 |
Sub-Array A |
| Disk 1 |
Disk 2 |
Disk 3 |
Sub-Array B |
When data is inserted into a RAID 0+1 array, it is first striped into one RAID 0 Sub-Array and then the entire Sub-Array is mirrored. Using our chart from above as an example, data would first be striped into RAID 0 Sub-Array A and then mirrored to Sub-Array B. It is important to note that if any disk from a RAID 0 Sub-Array is lost, the entire Sub-Array is lost (because there is no redundancy in RAID 0). For example, if Disk 4 fails, Sub-Array B as a whole fails. This is because the RAID controller views each Sub-Array as a single logical unit. The system will continue to operate without Sub-Array B but it is now reduced to a single level RAID 0. If any drive in Sub-Array A fails at this point, the entire system will fail.
The Raid 0+1 reconstruction process is nearly identical to the single level RAID 0 reconstruction process with the added complications of determining disk layout.
See our
RAID 0 recovery page for a detailed explanation. Gillware looks forward to helping you with your multi-level RAID 0+1 reconstruction needs.
To place an order please call our toll-free number.
Continue reading about RAID Arrays at one of our informational pages listed below.
