User's Manual

38 Understanding RAID Concepts
When a physical disk in a concatenated or spanned volume fails, the entire
volume becomes unavailable. Because the data is not redundant, it cannot be
restored by rebuilding from a mirrored disk or parity information. Restoring
from a backup is the only option.
Because concatenated volumes do not use disk space to maintain redundant
data, they are more cost-efficient than volumes that use mirrors or parity
information. A concatenated volume may be a good choice for data that is
temporary, easily reproduced, or that does not justify the cost of data
redundancy. In addition, a concatenated volume can easily be expanded by
adding an additional physical disk.
Figure 3-1. Concatenating Disks
• Concatenates n disks as one large virtual disk with a capacity of n disks.
• Data fills up the first disk before it is written to the second disk.
• No redundancy data is kept. When a disk fails, the large virtual disk fails.
• No performance gain.
• No redundancy.