User Capacity For Each Raid Level - Fujitsu Eternus2000 Manual

• RAID6 (striping with distributed double parities)
Store two different parities on different disk drives (double parities) to recover from up to two disk
drive failures.
A
A
E
I
M
HDD0
Figure 1.5

User Capacity for each RAID Level

User capacity varies according to the RAID level.
Table 1.1 shows the formula for user capacity computation.
Table 1.1
RAID level
RAID0
RAID1
RAID1+0
RAID5
RAID6
1. Actual number of disk drives can be installed depend on the ETERNUS2000 models.
P3AM-2512-03EN ETERNUS2000 disk storage system User Guide
Data writing request
A B C
B C
B C
F G
J P1
I, J, K, L
P1 P2
M, N, O, P M, N, O, P
HDD1 HDD2
Parity for data A to D: Parity1
Parity for data E to H: Parity1
Parity for data I to L:
Parity for data M to P: Parity1
RAID6 Concept
User Capacity for each RAID Level
Number of disk drives (*1)
2 to 16
2
4 to 32
3 to 16
5 to 16
Copyright 2009 FUJITSU LIMITED
D
D
Create parity data
P1
A, B, C, D
D
P1 P2
E, F, G, H E, F, G, H
P2
I, J, K, L K
N O
HDD3 HDD4
and Parity2
A, B, C, D
and Parity2
E, F, G, H
Parity1 I, J, K, L and Parity2
and Parity2
M, N, O, P
Formula for user capacity computation
Disk drive capacity x Number of disk drives
Disk drive capacity x Number of disk drives/2
Disk drive capacity x Number of disk drives/2
Disk drive capacity x
(Number of disk drives - 1)
Disk drive capacity x
(Number of disk drives - 2)
Chapter 1 Overview
P2
A, B, C, D
H
L
P
HDD5
A, B, C, D
E, F, G, H
I, J, K, L
M, N, O, P
1
7