Avago Technologies 3ware SAS 9750-4i - Manual (Page 23)

Understanding RAID Levels and Concepts
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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
2 RAID 0 or RAID 1