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AEC-6885 User's Manual
Appendix A About RAID
RAID (Redundant Array of Independent Disks) is a system composed of many hard
drives; that is, a pair of hard drives or more unite into a whole drive or an array. For
the system only one hard drive is revealed. 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 composition 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 allocated to each hard drive of the
array. Thus the access speed becomes quicker. The effect of RAID 0 is propor-
tioned 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 error 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 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 error tolerance.
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