User`s manual

AEC-6897/6897LP Manual

Appendix A About RAID

RAID (Redundant Array of Independent Disks) is a system composed of many hard

drives; that is, multiple physical drives form a single virtual drive to be recognized by

the system. The advantages of RAID technology are increasing the read/write speed

of a hard drive, achieving better data protection, and enlarging the capacity of a

single drive like Drive C, Drive D, etc. Different classes of RAID have different com-

position modes and different functions.

A-1 RAID 0 (Striping)

RAID 0 must be composed of a pair of hard drives at least. When data are written

into the whole hard drive, they will be equally striped and written into each hard

drive of the array. Thus the access speed becomes quicker. The effect of RAID 0 is

proportioned to the number of hard drives. More hard drives mean more read/write

heads, and therefore the speed is quicker. Though RAID 0 is quick in read/write

speed, it has no data redundancy, and accordingly has no fault tolerance.

It is suggested to compose RAID 0 with hard drives of the same capacity. Because

the capacity of striped disk array is the multiplication of the smallest hard drive

capacity with the number of hard drives. For example, a 100GB hard drive and two

120GB hard drives unite into RAID 0. The total capacity is 300GB (100GB×3).

A-2 RAID 1 (Mirroring)

RAID 1 must be composed of hard drives in even number. The RAID controller will

divide the hard drives into a pair, and write data simultaneously into the two hard

drives. The two hard drives contain the same data. When one hard drive’s data are

damaged, you can replace the failed hard drive, and the RAID controller will restore

the data by the backup on the other hard drive. For a single hard drive RAID 1 is the

best in fault tolerance.