Adaptec 2820SA User Guide - Page 68

RAID 1 Arrays, RAID 1 Enhanced Arrays, A RAID 1 Enhanced RAID 1E array-also known as - capacity

Get Adaptec 2820SA - Serial ATA II RAID Controller PDF manuals and user guides
UPC - 760884148969
View all Adaptec 2820SA manuals
Add to My Manuals
Save this manual to your list of manuals

Page 68 highlights

Appendix B: Understanding RAID ● 68 RAID 1 Arrays A RAID 1 array is built from two disk drives, where one disk drive is a mirror of the other (the same data is stored on each disk drive). Compared to independent disk drives, RAID 1 arrays provide improved performance, with twice the read rate and an equal write rate of single disks. However, capacity is only 50 percent of independent disk drives. If the RAID 1 array is built from different- sized disk drives, the free space, drive segment size is the size of the smaller disk drive, as shown in this figure. Drive Segment Size (Smallest Disk Drive) Disk Drive 1 250 GB Disk Drive 2 400 GB Disk Drives in Logical Drive Disk Drive 1 1 - 250 Disk Drive 2 1 - 250 Unused Space = 150 GB RAID 1 Logical Drive = 250 GB RAID 1 Enhanced Arrays A RAID 1 Enhanced (RAID 1E) array-also known as a striped mirror-is similar to a RAID 1 array except that data is both mirrored and striped, and more disk drives can be included. A RAID 1E array can be built from three or more disk drives-depending on the stripe size, the maximum number of disk drives ranges from eight to sixteen. In this example, the large bold numbers represent the striped data, and the smaller, non-bold numbers represent the mirrored data stripes. Disk Drive 1 400 GB Disk Drive 2 400 GB Disk Drive 3 400 GB Disk Drives in Logical Drive Disk Drive 1 1 3 4 6 Disk Drive 2 2 1 5 4 Disk Drive 3 3 2 6 5 RAID 1E Logical Drive = 600 GB

  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34
  • 35
  • 36
  • 37
  • 38
  • 39
  • 40
  • 41
  • 42
  • 43
  • 44
  • 45
  • 46
  • 47
  • 48
  • 49
  • 50
  • 51
  • 52
  • 53
  • 54
  • 55
  • 56
  • 57
  • 58
  • 59
  • 60
  • 61
  • 62
  • 63
  • 64
  • 65
  • 66
  • 67
  • 68
  • 69
  • 70
  • 71
  • 72
  • 73
  • 74
  • 75
  • 76
  • 77
  • 78
  • 79
  • 80
  • 81
  • 82
  • 83
  • 84
  • 85
  • 86
  • 87
  • 88
  • 89
  • 90
  • 91
  • 92
  • 93
  • 94
  • 95
  • 96
  • 97
  • 98
  • 99
  • 100
  • 101
  • 102
  • 103
  • 104
  • 105
  • 106
  • 107
  • 108
  • 109
Appendix B: Understanding RAID
●
68
RAID 1 Arrays
A RAID 1 array is built from two disk drives, where one disk drive is a
mirror
of the other (the
same data is stored on each disk drive). Compared to independent disk drives, RAID 1 arrays
provide improved performance, with twice the read rate and an equal write rate of single disks.
However, capacity is only 50 percent of independent disk drives.
If the RAID 1 array is built from different- sized disk drives, the free space, drive segment size is
the size of the smaller disk drive, as shown in this figure.
RAID 1 Enhanced Arrays
A RAID 1 Enhanced (RAID 1E) array—also known as a
striped mirror
—is similar to a RAID 1
array except that data is both mirrored
and
striped, and more disk drives can be included. A
RAID 1E array can be built from three or more disk drives—depending on the stripe size, the
maximum number of disk drives ranges from eight to sixteen.
In this example, the large bold numbers represent the striped data, and the smaller, non-bold
numbers represent the mirrored data stripes.
Disk Drive 2
Disk Drive 1
250 GB
400 GB
Drive Segment Size
(Smallest Disk Drive)
Disk Drive 1
Disk Drive 2
Disk Drives in Logical Drive
RAID 1 Logical Drive = 250 GB
1 – 250
1 – 250
Unused Space = 150 GB
Disk Drive 2
Disk Drive 1
400 GB
Disk Drives in Logical Drive
RAID 1E Logical Drive = 600 GB
400 GB
400 GB
Disk Drive 3
Disk Drive 2
Disk Drive 1
Disk Drive 3
1
3
2
3
4
5
6
1
2
6
4
5