Figure 2 Raid6-Fr Concept; Table 5 Raid Level Comparison - Fujitsu ETERNUS AF S3 Series Design Manual

2. Basic Functions
RAID Functions
●
RAID6-FR (Striping with Double Distributed Parity which Provides High-Speed Rebuild Capabilities)
Distributing multiple data groups and reserved space equivalent to hot spares to the configuration drives
makes it possible to recover from up to two drive failures. RAID6-FR requires less build time than RAID6.
Figure 2 RAID6-FR Concept
A
A
P2
K
P1
M, N, O
P1
X
FHS
Drive#0 Drive#1
■
Reliability, Performance, Capacity for Each RAID Level
Table 5 shows the comparison result of reliability, performance, capacity for each RAID level.
Table 5 RAID Level Comparison
RAID level
RAID0
RAID1
RAID1+0
RAID5
RAID5+0
RAID6
RAID6-FR
◎: Very good ¡: Good △: Reasonable ´: Poor
*1: Performance may differ according to the number of drives and the processing method from the host.
Data writing request
A B C
B C
Create parity data
P1 P2
B C
A, B, C A, B, C
J H
G, H, I
FHS
P2
R P, Q, R
M
P1 P2
S, T, U V, W, X V, W, X
V
FHS
Drive#2 Drive#3 Drive#4
RAID6-FR ((3D+2P) × 2 + 1HS)
Reliability
´
¡
¡
¡
¡
◎
◎
D
D
D E F
FHS
P1
L I
J, K, L
P1 P2
O P, Q, R M, N, O
FHS
S W
Drive#5 Drive#6 Drive#7
Parity for data A, B, C: P1
Parity for data D, E, F: P1
Parity for data G, H, I: P1
Parity for data J, K, L: P1
Parity for data M, N, O: P1
Parity for data P, Q, R: P1
Parity for data S, T, U: P1
Parity for data V, W, X: P1
:
Fast recovery Hot Spare: FHS
Performance (*1)
◎
¡
◎
¡
¡
¡
¡
23
Create parity data
P1 P2
FHS
D, E, F D, E, F
P2 P1
G
J, K, L G, H, I
N Q P
P2
S, T, U
T U
Drive#8 Drive#9 Drive#10
and P2
A, B, C A, B, C
and P2
D, E, F D, E, F
and P2
G, H, I G, H, I
and P2
J, K, L J, K, L
and P2
M, N, O M, N, O
and P2
P, Q, R P, Q, R
and P2
S, T, U S, T, U
and P2
V, W, X V, W, X
Capacity
◎
△
△
¡
¡
¡
¡
Design Guide