RAID 6 can tolerate the failure of two disks without data loss, while RAID 5 can only tolerate the failure of a single disk. This makes RAID 6 a better choice for environments where data protection is critical, such as enterprise servers and data centers.
RAID 6 stores two parity stripes, which means that it can still calculate the original data even if two disks fail. RAID 5 only stores a single parity stripe, so if two disks fail, the data is lost.