HP StorageWorks 1500cs Modular Smart Array - Manual (Page 64)

Drive arrays and fault-tolerance methods 64
RAID 1+0—drive mirroring
In a RAID 1+0 configuration, data is duplicated to a second drive.
When the array has more than two physical drives, drives are mirrored in pairs.
In each mirrored pair, the physical drive that is not busy answering other requests answers any read
requests that are sent to the array. (This behavior is called load balancing.) If a physical drive fails, the
remaining drive in the mirrored pair can still provide all the necessary data. Several drives in the array
can fail without incurring data loss, as long as no two failed drives belong to the same mirrored pair.
This fault-tolerance method is useful when high performance and data protection are more important than
the cost of physical drives.
NOTE: When there are only two physical drives in the array, this fault-tolerance method is often referred to
as RAID 1.
Advantages:
• Has the highest read performance of any fault-tolerant configuration.