LaCie 2big Quadra Enterprise Class
• D
esign
by
n
eil
P
oulton
RAID
User Manual
page 16
3.1.2. Concatenation
When disks are concatenated, their capacities are combined and
data is written to the primary disk in the array until is it full, and
then to successive disks (
Fig. 08
). Concatenation provides no per-
formance advantage or added measure of data safety. It is simply a
method of combining more than one physical disk into one volume
for greater overall capacity.
Concatenation allows full use of the capacity of all disks in the array
and most data can survive a disk failure. Only data on the failed disk
and data that is partially written on the failed disk and an operative
disk is lost.
Offers the maximum possible capacity by combining the capacities
of several drives into one large volume.
3.1.3. Safe (RAID 1)
In Safe mode (RAID 1), the two physical disks are mirrored together
so that one single logical volume mounts on the desktop (
Fig. 09
).
All data is saved simultaneously on each disk (the available capacity
cannot exceed the available capacity of the lowest-capacity single
disk). If one physical disk fails, the data is available immediately on
the second disk. No data is lost if one disk fails.
A
B
C
D
E
F
G
H
Disk 1
Disk 2
Disk 1
Disk 2
A1
B1
C1
D1
E1
A1
B1
C1
D1
E1
Fig. 08
Fig. 09
Applications
✦
Maximum data safety
✦
Safe reduces the total available capacity by 50% be-
cause two copies of the data are saved.
