User guide

Chapter 1 Overview
> 1.2 Configuration
ETERNUS DX60/DX80/DX90 Disk storage system User Guide
30
Copyright 2010 FUJITSU LIMITED
P3AM-3042-06ENZ0
• RAID6 (striping with distributed double parities)
Store two different parities on different disks (double parities) to recover from up to two disk
failures.
Figure 1.6 RAID6 concept
■ User capacity for each RAID level
User capacity varies according to the RAID level.
Table 1.1
shows the user capacity per disk. Table 1.2 shows the formula for calculating the user
capacity for each RAID level.
Table 1.1 User capacity per disk
*1: The above User Capacities are based on a 1MB = 1,024
2
Byte metric.
P2 M, N, O, P
P2 I, J, K, L
A
E
I
M
ABCD
Data writing request
B
F
J
P1
M, N, O, P
C
G
P1
I, J, K, L
D
P1
E, F, G, H P2 E, F, G, H
N
K
O
P1 A, B, C, D
H
L
P
P2 A, B, C, D
A B DC
Create parity data
HDD0 HDD1 HDD2 HDD3 HDD4 HDD5
Parity for data A to D: Parity1
A, B, C, D and Parity2 A, B, C, D
Parity for data E to H: Parity1 E, F, G, H and Parity2 E, F, G, H
Parity for data I to L: Parity1 I, J, K, L and Parity2 I, J, K, L
Parity for data M to P: Parity1 M, N, O, P and Parity2 M, N, O, P
Product name User Capacity per Disk (*1)
100GB SSD 92,672MB
200GB SSD 186,624MB
146GB SAS disk 135,936MB
300GB SAS disk 279,040MB
450GB SAS disk 419,072MB
600GB SAS disk 559,104MB
750GB Nearline SAS disk 702,976MB
1TB Nearline SAS disk 937,728MB
2TB Nearline SAS disk 1,866,240MB