EMC FC4700 manual

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EMC Fibre Channel Storage System Model FC4700 Configuration Planning Guide
RAID Types and Tradeoffs
Figure 2-7 Disk Space Usage in the RAID Configuration
A RAID 0 Group (nonredundant individual access array) provides all
its disk space for user files, but does not provide any high availability
features. For high availability, you can use a RAID1/0 Group
instead.
A RAID1/0 Group provides the best combination of performance
and availability, at the highest cost per Mbyte of disk space.
An individual unit, like a RAID 0 Group, provides no
high-availability features. All its disk space is available for user data,
as shown in the figure above.
EMC1820
RAID 5 Group RAID 3 Group
2nd disk
user and parity data
2nd disk
user data
3rd disk
user and parity data
3rd disk
user data
4th disk
user and parity data
4th disk
user data
1st disk
user and parity data
1st disk
user data
5th disk
user and parity data
5th disk
parity data
80% user data
20% parity data
RAID 1/0 Group
2nd disk
user data
3rd disk
user data
4th disk
user data
6th disk
user data
1st disk
user data
5th disk
user data
50% user data
50% redundant data
RAID 0 Group
(nonredundant array)
2nd disk
user data
3rd disk
user data
1st disk
user data
100% user data
2nd disk
user data
1st disk
user data
Disk Mirror (RAID 1 mirrored pair)
50% user data
50% redundant data
User data
Individual Disk Unit
100% user dataReserved
Hot Spare
No user data