EMC Clariion RAID-6 requirements and limitations

Here are some requirements and limitations related to using the RAID-6 technology on the EMC Clariion platforms.

• RAID-6 is only supported with Flare Release 26 and above on Clariion systems.
• Flare 26 only works on the EMC Clariion CX300, CX500, CX700, all CX3-xx platforms and all CX4-xxx platforms.|
• Any systems running below Flare Release 26 (example Release 13, 16, 19, 24) are not compatible to run RAID-6 (Clariion Systems like CX200, CX400 and CX600).

• Minimum disk required to support RAID-6 with Clariion systems is 2 or 4 or 6 or 8 or 14 data disks with 2 Parity disks (Your typical configuration would look like 2D+2P or 4D+2P or 6D+2P or 8D+2P or 14D+2P, where D = Data Disk and P = Parity Disk)
• To configure RAID-6, you will need even number of disk drives in the RAID Group that you are trying to configure.
• RAID-6 is supported on either EFD (Enterprise Flask Disk) or Fiber (FC) or ATA or SATA drives on EMC Clariion Systems.
• RAID-6 Raid group (RAID SET) can be implemented within an enclosure or expanded beyond a single enclosure
• RAID-6 can co-exist in the same DAE (disk array enclosure) as a RAID-5 and/or RAID-1/0 and/or other RAID types.
• RAID-6 supports global hot sparing like other RAID technologies.
• Supports MetaLUN expansion through concatenated or striped expansion only if all the meta member LUNs are RAID-6 devices (LUNs).
• RAID-6 configuration is possible through Navisphere and naviseccli only.
• With RAID-6 traditionally supported CLI interfaces like Java CLI and Classic CLI have been retired.
• Defragmentation with RAID-6 is currently not supported on Flare Release 26.
• You cannot add new drives to an existing RAID-6 LUN, but you can expand the LUN through RAID-6 MetaLUN technology. Example of this will be, if you have a 6D+2P RAID-6 set and would like to add 16 more drives to the same RAID Group, you cannot accomplish it, but if you manage to create either 2 sets of 6D+2P or 1 set of 14D+2P, and then run a MetaLUN concatenate, you will be able to necessarily achieve the same end result.
• You can have Clariion systems with various different RAID group technologies in the same global domain, but again from a management perspective certain traditional CLI interfaces will not work with RAID-6.
• Using the Virtual LUN Technology with Flare Release 26, now customers can migrate various LUNs (RAID-5, RAID-1/0) to RAID-6 technology. The technology allows the new RAID-6 LUN to assume the exact identity of the previous LUN making the migration process much easy.
• Traditional replication and copy software’s like SANCopy, SnapView, MirrorView, and RecoverPoint are all supported for RAID-6 technology.
• Never use RAID-6 technology with a mix of EFD, FC, ATA and SATA drives in the same RAID Group.
• Never use RAID-6 technology with a mix of various drive speeds like 15K or 10K or 7.2K RPM, drive speed should be exactly similar.

• Oh the most important note: 2 drive failures in the same RAID Group and no data loss or data unavailable (DU / DL), making this a very robust RAID technology. There are some performance overhead related to use of RAID-6 systems with small and random writes. While there is an added penalty with Row Parity and Diagonal Parity calculations on the Clariion.

If you would like to see any further post on RAID-6 workings on Clariion Platforms, please feel free to leave a comment.