Disk spanning allows multiple disk drives to function like one big drive. Spanning overcomes lack of disk space and simplifies storage management by combining existing resources or adding relatively inexpensive resources. For example, four 60 Gbyte disk drives can be combined to appear to the operating system as one single 240 Gbyte drive.
Disk spanning alone does not provide reliability or performance enhancements. Spanned logical drives must have the same stripe size and must be contiguous. In Figure 2.3, two RAID 1 arrays are turned into a RAID 10 array.
Figure 2.3 Disk Spanning
MegaRAID Controller
|
| Data Flow |
|
RAID 1 |
| RAID 1 |
|
Disk 1 | Disk 2 | Disk 3 | Disk 4 |
Segment 1 | Segment 1 | Segment 2 | Segment 2 |
Segment 3 | Segment 3 | Segment 4 | Segment 4 |
Segment 5 | Segment 5 | Segment 6 | Segment 6 |
|
| RAID 0 |
|
The controller supports a span depth of eight. This means that eight
RAID 1, 3, or 5 arrays can be spanned to create one logical drive.
RAID Overview |
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