LSI 3ware 9750 User Manual page 22

Chapter 1. Introducing the LSI 3ware SATA+SAS RAID Controller Card
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Figure 6. RAID 10 Configuration Example
RAID 50
RAID 50 is a combination of RAID 5 and RAID 0. This array type provides
fault tolerance and high performance. RAID 50 requires a minimum of six
drives.
Several combinations are available with RAID 50. For example, on a 12-port
controller, you can have a grouping of three, four, or six drives. A grouping of
three means that the RAID 5 arrays used have three disks each; four of these
3-drive RAID 5 arrays are striped together to form the 12-drive RAID 50
array. On a 16-port controller, you can have a grouping of four or eight drives.
No more than four RAID 5 subunits are allowed in a RAID 50 unit. For
example, a 24-drive RAID 50 unit may have groups of 12, eight, or six drives,
but not groups of four or three (see Figure 7).
In addition, RAID 50 arrays offer a higher degree of fault tolerance than
RAID 1 and RAID 5, because the array can sustain multiple drive failures
without data loss. For example, in a 12-drive RAID 50 array, one drive in each
RAID 5 set can fail and the array continues to function. Note that if two or
more drives in a RAID 5 set fail, all of the data is lost.
3ware SATA+SAS RAID Controller Card Software User Guide, Version 10.2