AMCC 9500S User Manual

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Chapter 1. Introduction to the 3ware Command Line Interface
16
3ware Serial ATA RAID Controller CLI Guide 
Hot Spare
A hot spare is a single drive, available online, so that a redundant unit can be 
automatically rebuilt in case of drive failure. 
Determining What RAID Level to Use
Your choice of which type of RAID unit (array) to create will depend on your 
needs. You may wish to maximize speed of access, total amount of storage, or 
redundant protection of data. Each type of RAID unit offers a different blend 
of these characteristics.
The following table provides a brief summary of RAID type characteristics. 
                                      
You can create one or more units, depending on the number of drives you 
have installed.
Table 2: RAID Configuration Types
RAID Type
Description
RAID 0
Provides performance, but no fault tolerance.
RAID 1
Provides fault tolerance and a read speed advantage over non-
RAID disks.
RAID 5
This type of unit provides performance, fault tolerance, and high 
storage efficiency. RAID 5 units can tolerate one drive failing 
before losing data.
RAID 6
Provides very high fault tolerance with the ability to protect 
against two consecutive drive failures. Performance and 
efficiency increase with higher numbers of drives. 
RAID 10
A combination of striped and mirrored units for fault tolerance 
and high performance.
RAID 50
A combination of RAID 5 and RAID 0. It provides high fault 
tolerance and performance.
Single Disk
Not a RAID type, but supported as a configuration. 
Provides for maximum disk capacity with no redundancy.
Table 3: Possible Configurations Based on Number of Drives 
# Drives
Possible RAID Configurations
1
Single disk or hot spare
2
RAID 0 or RAID 1