Figure 4.6 Raid6 Concept; Table 4.1 User Capacity For Each Raid Level - Fujitsu ETERNUS DX80 S2 Overview

Chapter 4 System Configuration
4.1 RAID Levels
●
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

A
A
E
I
M
HDD0
■
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
RAID level
RAID0
RAID1
RAID1+0
RAID5
RAID5+0
RAID6
*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.
Data writing request
A B C D
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:
Parity for data E to H:
Parity for data I to L:
Parity for data M to P:
Reliability
Poor
Good
Good
Good
Good
Very Good
36
ETERNUS DX80 S2/DX90 S2 Disk storage system Overview
Copyright 2013 FUJITSU LIMITED
Create parity data
D
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
P1 and P2
A, B, C, D A, B, C, D
P1 and P2
E, F, G, H E, F, G, H
P1 and P2
I, J, K, L I, J, K, L
P1 and P2
M, N, O, P M, N, O, P
Performance (*1) Capacity
Very Good Very Good
Good Reasonable
Very Good Reasonable
Good
Good
Good
P2
A, B, C, D
H
L
P
HDD5
Good
Good
Good
P3AM-4812-11ENZ0