To achieve the HIGHEST level of redundancy while configuring 10 web servers with up to four hard disks each, which RAID configuration should be used?

To achieve the highest level of redundancy in a server setup with multiple web servers and multiple hard disks per server, RAID 6 is the most suitable configuration. RAID 6 provides dual parity, which means it can withstand the failure of two hard disks simultaneously without losing any data. This is particularly beneficial in environments where uptime is critical, as it allows for greater fault tolerance.

In a setup with ten web servers, having RAID 6 ensures that not only is data protected against single drive failures, but also against the failure of two drives in the same RAID group. This is especially important when multiple disks are involved, as RAID 6 allows for the continued operation of the server even under hardware failures, thereby maintaining availability and reliability of the web services.

Additionally, RAID 6 utilizes the disks more effectively compared to simple mirroring setups, as it spreads data and parity information across all disks, which can help prevent data loss and improve performance for read operations, while still maintaining redundancy.

While RAID 10 also offers high redundancy and combines the benefits of both RAID 0 (striping) and RAID 1 (mirroring), it requires a minimum of four disks and offers only single parity, meaning it can withstand a single disk failure in each mirrored pair.