Avago Technologies MegaRAID SATA 150-4 (523) - Manual (Page 31)

RAID Components and Features 2-9
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Figure 2.4 Disk Spanning (RAID 10) Example
Note: Spanning two contiguous RAID 0 logical drives does not
produce a new RAID level or add fault tolerance. It
increases the size of the logical volume and improves
performance by doubling the number of spindles.
Disk Spanning for RAID 10 or RAID 50. Table 2.2 describes how to
configure RAID 10 and RAID 50 by spanning. The logical drives must
have the same stripe size, and the maximum number of spans is eight.
The full drive size is used when you span logical drives; you cannot
specify a smaller drive size.
2.4.12 Hot Spares
A hot spare is an extra, unused disk drive that is part of the disk
subsystem. It is usually in standby mode, ready for service if a drive fails.
Hot spares permit you to replace failed drives without system shutdown
or user intervention. MegaRAID 320 controllers can implement automatic
and transparent rebuilds of failed drives using hot spare drives, providing
a high degree of fault tolerance and zero downtime.
Note. When running RAID 0 and RAID 5 logical drives on the
same set of physical drives (a sliced configuration), a
rebuild to a hot spare does not occur after a drive failure
until the RAID 0 logical drive is deleted.
Table 2.2 Disk Spanning for RAID 10 and RAID 50
Level Description
10 Configure RAID 10 by spanning two contiguous RAID 1 logical drives.
The RAID 1 logical drives must have the same stripe size.
50 Configure RAID 50 by spanning two contiguous RAID 5 logical drives.
The RAID 5 logical drives must have the same stripe size.
60 Gbytes/s 60 Gbytes/s
Can Be Accessed as
One 120 Gbyte/s Drive
60 Gbytes/s 60 Gbytes/s
Can Be Accessed as
One 120 Gbyte/s Drive