This is the latest recommendation from Dell Equallogic, found in Firmware 6.0 Release Note:

Beginning with this release, the Group Manager GUI no longer includes the option for configuring a group member to use RAID 5 for its RAID policy. RAID 5 carries higher risks of encountering an uncorrectable drive error during a rebuild, and therefore does not offer optimal data protection. Consequently, Dell recommends against using RAID 5 for any business-critical data.

RAID 5 may still be required for certain applications, depending on performance and data availability require-ments. To allow for these scenarios, you may still use the CLI to configure a group member to use RAID 5.

For a complete discussion of RAID policies on PS Series systems, review the Dell Technical Report titled PS Series Storage Arrays: Choosing a Member RAID Policy, which can be downloaded from either of the following locations:

• www.equallogic.com/resourcecenter/documentcenter.aspx

• en.community.dell.com/techcenter/storage/w/wiki/equallogic-tech-reports.aspx

In addition, Dell recommends against using RAID configurations that do not use spare drives. You should convert all group member that are using a no-spares RAID policy to a policy that uses spare drives.

Known Issues and Limitations

The following restrictions and known issues apply to this version of the PS Series Firmware. For information about known issues and restrictions from other releases, see the Release Notes for those versions. For issues about Dell EqualLogic FS Series Appliances, refer to the Dell EqualLogic FS Series Appliances Release Notes. For issues and limitations pertaining to host operating systems and iSCSI initiators, refer to the iSCSI Initiator and Operating System Considerations document.

RAID Conversion From No-Spares To Spares Does Not Work
RAID conversion from a no-spares policy to a spares policy appears to work, but it actually converts to no-spares, resulting in no change. (Funny )