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Table Of Contents
- 1 Introduction to member RAID policies
- 2 RAID policy availability and performance comparisons
- 3 Setting the member RAID policy
- 4 Displaying the RAID level space distribution
- 5 PS Series array disk layout
- 6 Converting or migrating from a member RAID policy
- 7 Summary
- A 12-Disk PS Series array RAID configurations
- B 14-Disk PS Series array RAID configurations
- C 16-Disk PS Series array RAID configurations
- D 48-Disk PS Series array RAID configurations
- E 42 or 84-disk PS Series RAID configurations
- F Technical support and resources
5 Dell PS Series Storage: Choosing a Member RAID Policy | TR1020 | v 4.7
1.1 RAID policy descriptions
The following RAID policies are available using the PS Series Group Manager GUI or the CLI:
RAID 6 – One or more RAID 6 sets, with one or two spare disks. RAID 6 delivers multiple parity
protection and provides the highest availability of any of the supported RAID policies because it can
accommodate two drive failures at any one time. RAID 6 offers reliable performance for workloads
consisting mainly of sequential reads and writes, or random reads. For workloads consisting mainly of
random write operations, RAID 10 would be a better RAID policy choice due to the performance cost
of extra writes to parity within the RAID 6 set during write operations. Unlike with the other RAID
policies, a RAID 6 set can survive up to two drive failures at one time. The RAID set remains
degraded until both failed disks are replaced and data reconstruction is complete.
RAID 10 – Striping on top of multiple RAID 1 (mirrored) sets, with one or two spare disks (depending
on the total number of disks in the array). RAID 10 provides excellent performance for random writes,
in addition to high availability. RAID 10 also offers the best performance when the RAID set is
degraded. However, since the disks are mirrored, RAID 10 provides the least capacity and highest
cost.
RAID 50 – Striping on top of multiple RAID 5 (distributed-parity) sets, with one or two spare disks
(depending on the total number of disks in the array). RAID 50 provides a balance of performance,
availability, and capacity. However, RAID 50 offers lower performance than RAID 10 when the RAID
set is degraded and is not recommended for arrays with disks 1TB or greater.
RAID 5 - One or more RAID 5 sets, with at least one spare disk. RAID 5 is similar to RAID 50, with
more capacity but significantly lower reliability and availability when compared with the other RAID
types. RAID 5 also suffers more performance impact than RAID 10 and RAID 50 when the RAID set
is degraded.
Note: RAID 5 should only be used for non-critical data. RAID 5 is only mentioned in this document to
accommodate older systems.
For the purposes of this document, RAID 50 was used as a baseline to compare various aspects of the PS
Series RAID options. RAID 50 was chosen because it has historically been popular with users due to its good
balance of capacity and performance.