Fujitsu Eternus DX80 S2 - Figure 4.6 RAID6 Concept; Table 4.1 User Capacity for each RAID Level

Chapter 4 System Configuration
4.1 RAID Levels
ETERNUS DX80 S2/DX90 S2 Disk storage system Overview
Copyright 2013 FUJITSU LIMITED P3AM-4812-11ENZ0
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● RAID6 (striping with distributed double parities)
RAID6 stores two different parities on different drives (double parities) to recover from up to two drive
failures.
Figure 4.6 RAID6 concept
■ Reliability, performance, capacity for each RAID level
Table 4.1 shows the comparison result of reliability, performance, capacity for each RAID level.
Table 4.1 User capacity for each RAID level
*1: Performance may differ according to the number of drives and the processing method from the host.
■ Recommended RAID level
Select the appropriate RAID level according to the usage.
• Recommended RAID level is RAID1, RAID1+0, RAID5, RAID5+0 and RAID6.
• For read and write performance, RAID1+0 configuration is recommended.
• For read only file servers and backup servers, RAID5, RAID5+0, or RAID6 can also be used. However, if the
drive fails, note that data restoration from parities and rebuilding process may result in a loss in
performance.
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:
Parity for data E to H:
Parity for data I to L:
Parity for data M to P:
P1
A, B, C, D and P2 A, B, C, D
P1 E, F, G, H and P2 E, F, G, H
P1 I, J, K, L and P2 I, J, K, L
P1 M, N, O, P and P2 M, N, O, P
RAID level Reliability Performance (*1) Capacity
RAID0 Poor Very Good Very Good
RAID1 Good Good Reasonable
RAID1+0 Good Very Good Reasonable
RAID5 Good Good Good
RAID5+0 Good Good Good
RAID6 Very Good Good Good