User`s manual

AEC-6897/6897LP Manual
45
It is suggested to compose RAID 1 with hard drives of the same capacity. Because
the capacity of mirrored disk array is that of the smallest hard drive. For example, a
100GB hard drive and a 120GB one unite into RAID 1. The total capacity is 100GB.
A-4 RAID 0+1 (Striping/Mirroring)
A-3 RAID 5 (Striping with Rotating Parity)
RAID 5 must be composed of three hard drives at least. The parity data of RAID 5
are not fixed in the same hard drive, but stored in every hard drive in turn. Accord-
ingly, it is called rotating parity. After the RAID controller calculates the parity check-
ing data by XOR, the parity checking data will be written into each hard drive along
with data, so the overall performance is slower than RAID 0. RAID 5 can provide
higher fault tolerance.
RAID 0+1 is the combination of striping and mirroring. It has the advantages of two
RAID classes. The RAID controller allocates the writing of data equally among some
hard drives, and in the meantime backs up the data onto other hard drives. Accord-
ingly, it has the advantages of fault tolerance and quick read/write speed. RAID 0+1
needs at least 4 hard drives in even number. Its calculation of capacity is the same
as RAID 1. A half of the capacity is used for backup. It takes the smallest hard drive
capacity as the calculation basis. For example, four 100GB hard drives unite into
RAID 0+1. The total capacity is 200GB.
It is suggested to compose RAID 5 with hard drives of the same capacity. The
capacity of striped disk array with rotating parity is the multiplication of the smallest
hard drive capacity with the number of hard drives minus one. For example, a 100GB
hard drive and two 120GB hard drives unite into RAID 5. The total capacity is 200GB
(100GB×2).