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Choosing a RAID Policy

When selecting a RAID policy, you should consider the level of data protection you require, as well as I/O performance, capacity needs, and the types of drives contained in your PS Series array. The table below summarizes best practices for RAID policy selection.

Table: RAID Policies

RAID
Policy

Recommended Usage Scenarios

Recommended Drive Configurations

RAID 10

Applications and workloads requiring the highest levels of I/O performance for random writes.

Systems containing 10K and 15K RPM drives.

RAID 6

Applications requiring the highest levels of data protection and reliability.

Situations in which I/O performance for random writes is not a key factor.

Systems containing 7200 RPM SATA or Nearline SAS (NL-SAS) drives.

Systems containing 24 or more drives.

RAID 6
Accelerated

Optimizes the use of solid-state drives for critical data.

Supported only on arrays that contain both solid state (SSD) and hard disk (HDD) drives.

For these systems, it is the only available RAID policy. It is not a user-selectable option.

RAID 50

Applications requiring an optimal combination of performance, availability, and capacity.

Systems containing fewer than 24 drives.

Systems containing 10K and 15K RPM drives.

RAID 5

Dell recommends not using RAID 5 for any business-critical data.

RAID 5 carries higher risks of encountering an uncorrectable drive error during a rebuild, and therefore does not offer optimal data protection.

RAID 5 can only be configured using the CLI.

None.

For more information about RAID policies on PS Series systems, review the Dell Technical Report entitled, PS Series Storage Arrays: Choosing a Member RAID Policy, which you can download from either of the following locations:

dellstorage.com/resources/document-center.aspx
en.community.dell.com/techcenter/storage/w/wiki/equallogic-tech-reports.aspx

Table: RAID Level Characteristic Comparison compares the performance of the supported RAID levels for different workload requirements.

Table: RAID Level Characteristic Comparison

Workload Requirement

RAID 5

RAID 6

RAID 10

RAID 50

Capacity

Excellent

Good

Average

Good

Availability

Poor

Excellent

Good

Fair

Sequential reads

Excellent

Excellent

Excellent

Excellent

Sequential writes

Good

Good

Good

Good

Random reads

Excellent

Excellent

Excellent

Excellent

Random writes

Good

Fair

Excellent

Good

Performance impact of drive failure or RAID reconstruction

Longest

Longest

Shortest

Medium


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