Disk Spanning
Disk spanning lets multiple drives function like one big drive. Spanning overcomes a lack of disk space and simplifies storage management by combining existing resources or adding relatively inexpensive resources. For example, you can combine four 20-GB drives to appear to the operating system as a single 80-GB drive.
Spanning alone does not provide reliability or performance enhancements. Spanned virtual drives must have the same stripe size and must be contiguous. In the following figure, RAID 1 drive groups are turned into a RAID 10 drive group.
NOTE Make sure that the spans are in different backplanes, so that if one span fails, you do not lose the whole drive group.
Figure 10. Example of Disk Spanning
Spanning two contiguous RAID 0 virtual drives does not produce a new RAID level or add fault tolerance. It increases the capacity of the virtual drive and improves performance by doubling the number of spindles.
Spanning for RAID 10, RAID 50, and RAID 60
The following table describes how to configure RAID 10, RAID 50, and RAID 60 by spanning. The virtual drives must have the same stripe size, and the maximum number of spans is 8. The full drive capacity is used when you span virtual drives; you cannot specify a smaller drive capacity.
See Configuring Storage, for detailed procedures for configuring drive groups and virtual drives, and spanning the drives.
NOTE In a spanned virtual drive (RAID 10, RAID 50, and RAID 60) the span numbering starts from Span 0, Span 1, Span 2, and so on.