A RAID array is a setup of two or more hard drives that have been synchronized to provide protection against data. RAID is a great way to add additional security and redundancy to a computer workstation. The 12Gb/s SAS is designed for backward compatibility with 6Gb/s and 3Gb/s SAS/SATA hard drives.
Mac OS X includes a software-based RAID solution as part of its file system.The difference between the two is that RAID 4 stores parity information on a dedicated disk, while RAID 5 distributes the parity information. As with RAID 4, data is striped across the multiple component disks in the RAID at the block level. A RAID level that uses a combination of striping and parity to enhance the security of data storage.RAID 5 is a special case, though, it only needs addition in the Galois field GF(2).
RAID 5 can be seen as a special case of a Reed-Solomon code. It needs at least four disks (two disks for the capacity, two disks for redundancy). It adds an additional parity block to a RAID 5 array. RAID level 6 was not an original RAID level.This should not be a problem if your NAS is less than 5-6 years old, because SMB 3.0 was introduced in 2012.
How To Fix The macOS Catalina NAS Connection Failure The key is to set your NAS to use SMB 3.0 or later.Btrfs RAID 5/6 Code Found to Be Very Unsafe and Will Likely Require a Rewrite () 87 points by pantalaimon on.