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4 Dell PS Series Storage: Choosing a Member RAID Policy | TR1020 | v 4.7
1 Introduction to member RAID policies
PS Series arrays include redundant, hot-swappable components- for example physical disks, control
modules, fans, and power supplies - for a no-single-point-of-failure configuration. Along with redundant
hardware, PS Series arrays support several different RAID types with each type optimized to maximize
performance of the PS SAN architecture. When an array is added as a member to a PS Series group, the
RAID policy for that member is chosen. Depending on the PS Series array model and number of disks in the
array, RAID characteristics are implemented with various numbers of disks dedicated to data, parity, mirrors,
and hot spares.
The RAID policy choices for a member consist of RAID 6, RAID 10, RAID 50 and RAID 6 Accelerated (Hybrid
arrays only).
The table below lists the different RAID configurations in PS Series firmware v5.2.x and higher, options
supported with PS Series arrays, and when a RAID policy is a best practice.
RAID configurations and best practices
RAID Policy
Configurable in GUI
Configurable in CLI
Best practice for business critical
data?
RAID 6
Yes
Yes
Yes
RAID 10
Yes
Yes
No for HDD or SSD larger than 6 TB.
RAID 50
Yes
1
Yes
No for 7.2K disks 1 TB and larger
RAID 50
Yes
1
Yes
Yes 10K, 15K, SATA or NL-SAS < 1 TB
RAID 5
No
Yes
2
No
1
RAID 50 is not available using the GUI on PS6610 arrays
2
RAID 5 is only available via the PS command line
Since the release of PS Series Firmware version 6.0, RAID 5 is no longer an option in the Group Manager
GUI. In the PS Series, RAID 50 actually is preferred over RAID 5 because of the underlying disk set
configuration as described in the Appendix C.1 and C.2.
In addition, RAID 50 is not preferred for arrays with 1 TB or larger HDD disks. This change is the result of the
growing Class-2 HDD capacities and the degree of data protection that different RAID policies offer. RAID 6
and RAID 10 offer significantly higher levels of resiliency with very high capacity disks. This document shows
examples of these differences and discusses options for choosing an appropriate RAID policy.
Note: RAID 6 is the Dell recommendation for PS Series arrays populated with SATA or NL-SAS disks 1 TB
or larger and SSD or HDD 6 TB or larger. RAID 6 minimizes the risk of data loss during a RAID
reconstruction thereby maximizing protection of the RAID set. Therefore, this recommendation is strongly
encouraged for ALL customers when choosing a RAID policy for their arrays.
Existing configurations that use high capacity disks are encouraged when starting a migration plan that
follows the best practices described in this document. Refer to “Converting or migrating from a member RAID
policy”_Converting_or_Migrating for details.