How many drives are typically required for RAID 10?

RAID 10, also known as RAID 1+0, requires a minimum of four drives to function correctly. This configuration combines the features of RAID 1 (mirroring) and RAID 0 (striping). In RAID 10, data is split across multiple drives for performance (due to striping), while also maintaining redundancy through mirroring.

Here’s how it works: you need at least two pairs of drives. Each pair mirrors its data, thus providing fault tolerance, while the striping across these pairs improves read and write performance. This means that if one drive fails in each mirrored pair, the data remains intact as it is still available from the other drive in that pair. However, if fewer than four drives are used, the RAID 10 array cannot be formed as it will not meet the minimum requirements for both mirroring and striping.

With fewer than four drives, other configurations like RAID 0 or RAID 1 would be applicable, but they would not provide the same balance of redundancy and performance that RAID 10 offers. Therefore, to achieve the desired functionality of a RAID 10 setup, a minimum of four drives is necessary.