I believe it is because the arrangement of the first six letters in the top alphabet row of a standard keyboard QWERTY goes way back. The layout was created in 1873 when Christopher Latham Sholes made improvements to his earlier typewriter models in order to design a quicker and more efficient typewriter for E. Remington and Sons.
The RAID 1 is a category of the redundancy array of independent disks and drives. It is known as disk mirroring. It stores identical data to pair of drives. Its primary use is for redundancy, if a drive fails, the system can still access data from other drives and when the drive is replaced with another, all the copies of data is placed in the new drive, either from other disks or from a backup.