Why Use RAID-1+0?

RAID-1+0 is a fault-tolerant flavor of RAID that can be understand as “RAID-0 striped pair of RAID-1 mirror sets”.

RAID-1+0 enhances the fault tolerance of RAID-5 by allowing a drive to fail in each mirror set.

• Offers very good performance.
• Less efficient use of space (50% for a 4-drive setup).
• Tolerates the failure of all but one drives in each mirror set.
• Can be extended to higher fault tolerance, such as 3 drives in each mirror set.
• Can be restored to fault tolerance quickly by replacing a failed drive.

With four 5TB drives, one can have a 15TB RAID-5, or a 10TB RAID-1+0. For most users, RAID-5 is much more attractive (50% more capacity and speed).

RAID-1+0 requires at least 4 drives: a stripe of two mirror set pairs. In a 4-drive configuration, one drive can fail in each mirror, but failure of both drives in the same mirror kills the RAID. Thus it is significantly more fault tolerant than a RAID-5, but there is no guarantee that a 2nd failure won’t occur in the same mirror set.

RAID-1+0 vs RAID-5 capacity with 4 X 5TB drives: 50% vs 75% of total drive capacity

RAID 1+0 can be extended to use more drives. With 6 drives, a striped 3-way mirror set can be created; this allows the failure of up to two drives in each mirror set, but capacity is now only 33% of the total drive capacity. With 8 drives, 25%.

Creating a RAID volume in SoftRAID