Avago Technologies 3ware SAS 9750-16i4e - Manual (Page 22)

Chapter 1. Introduction to the 3ware Command Line Interface
14 3ware SATA+SAS RAID Controller Card CLI Guide, Version 10.2
structure. Higher data transfer rates are achieved by leveraging TwinStor
technology and striping the arrays.
In addition, RAID 10 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 10 array, up to 6 drives
can fail (half of each mirrored pair) and the array continues to function. Note
that if both halves of a mirrored pair in the RAID 10 array fail, all of the data
is lost.
Figure 5. 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 6).
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.