LSI Corporation
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12Gb/s MegaRAID SAS Software User Guide
March 2014
Chapter 2: Introduction to RAID
Components and Features
Figure 5 Example of Distributed Parity (RAID 5)
2.1.11
Disk Spanning
Disk spanning allows multiple 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 20-GB drives can be combined 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 6 Example of Disk Spanning
Spanning two contiguous RAID 0 virtual drives does not produce a new RAID level or add fault tolerance. It does
increase the capacity of the virtual drive and improves performance by doubling the number of spindles.
Spanning for RAID 00, RAID 10, RAID 50, and RAID 60
The following table describes how to configure RAID 00, 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
for detailed procedures for configuring drive groups and virtual drives, and spanning the drives.
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Summary of Contents for ThinkServer RD650
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