73
A
A
K
K
7
7
7
7
-
-
6
6
0
0
0
0
M
M
a
a
x
x
O
O
n
n
l
l
i
i
n
n
e
e
M
M
a
a
n
n
u
u
a
a
l
l
Logical Drive
Block 8
Block 7
Block 6
Block 5
Block 4
Block 3
Block 2
Block 1
Block 8
Block 7
Block 6
Block 5
Block 4
Block 3
Block 2
Block 1
Block 8
Block 7
Block 6
Block 5
Block 4
Block 3
M
M
i
i
r
r
r
r
o
o
r
r
i
i
n
n
g
g
(
(
R
R
A
A
I
I
D
D
1
1
)
)
Block 1
RAID level 1 uses at least two duplicate hard drives and store the exact
same blocks of information between them. This is the slowest form of
fault tolerance because the data has to be replicated onto two disks at
the same time. However, this is the simplest way to provide high
reliability.
Block 2
If one of the mirrored drives suffers a mechanical failure or does not
respond, the remaining drive will continue to serve and provide correct
data. If one drive has a physical sector error, the mirrored drive will
continue to function.
Physical Disks
Mi
rr
ori
n
g
Due to redundancy, the drive capacity of the array is half the total drive
capacity. For example, two 40GB drives that have a combined capacity
of 80GB would have 40GB of usable storage. With drives of different
capacities, there may be unused capacity on the larger drive. RAID 1
increases cost as it takes twice as much hard drives to build our arrays.
