Rapid RAID Recovery

The Rapid Raid Recovery feature increases the speed with which a redundant unit can be made redundant again when a rebuild is required. It can also increase the speed of verification or initialization that may occur in the event of an unclean shutdown.

Rapid RAID Recovery is possible because the firmware maps the unit, and tracks the areas of the unit where write activity occurs. Then, if a rebuild, initialization, or verify is required, the controller only has to address the active areas. The fewer active areas, the faster the rebuild, initialize or verify.

Since the units are mapped out and tracked from the creation of the unit, this feature can only be enabled during unit creation. Also, once disabled, it cannot be re-enabled.

The more space is available on a unit, the more benefit you will see in the event of a rebuild, if you enable Rapid RAID Recovery. If all of a unit’s capacity is being used, you may not see reduction of rebuild speed when using Rapid RAID Recovery. However, Rapid RAID Recovery still provides benefits to unit verification and to initialization after an unclean shutdown, regardless of the disk usage.

Possible settings are All (labeled Fast Rebuild/Shutdown in 3BM), Rebuild or Disable. All will apply the policy to both rebuilds and unclean shutdowns. Rebuild will apply only to rebuilds. Disable means that rebuilds, initializations and verifies will take place on the entire unit, not just the active sections. The default setting is All.

There is some system overhead from setting rapid recovery to All. If you have a BBU, you can set rapid recovery to Rebuild, as a BBU provides protection against data loss in the event of an unclean shutdown.

Some limitations of Rapid RAID Recovery:

Units with Rapid RAID Recovery enabled will not be readable if moved to controllers using pre-9.5.1 firmware. If you wish to move the unit to a controller with pre-9.5.1 firmware, you must first disable Rapid RAID Recovery.

Units created on controllers with pre-9.5.1 firmware will not be able to take advantage of Rapid RAID Recovery when the controller is updated to 9.5.1 or later. These units will show Rapid RAID Recovery as disabled.

Since the Rapid RAID Recovery feature tracks areas of the unit where write activity occurs, file systems such as FAT, FAT32, NTFS, and XFS are ideally suited to this implementation. For details on other file systems, search the LSI KnowledgeBase for keyword 15462 at :http://kb.lsi.comProtection against unclean shutdowns to provide a fast verification and initialization is the same regardless of the file system.

Changing or disabling Rapid RAID Recovery

Rapid RAID Recovery can only be enabled (that is - set to All or Rebuild) when the unit is created. You can change between All and Rebuild at any time. However, if you disable Rapid RAID Recovery, you cannot then enable it.

To change or disable Rapid RAID Recovery for an existing unit through 3DM2

1	Choose Management >> Controller Settings from the menu bar in 3DM2.

2	In the Unit Policies section of the Controller Settings page, select All, Rebuild, or Disable from the Rapid RAID Recovery dropdown menu.

3	Click OK when 3DM2 asks you to confirm your selection.

The page refreshes, and a message at the top confirms the change that you have made.

Related Topics: Enabling and Disabling the Unit Write Cache; Working with Read Cache Settings; Enabling or Disabling Auto-Verify for a Unit; Setting Overwrite ECC (Continue on Source Error When Rebuilding); Enabling and Disabling Queuing for a Unit; Setting the StorSave Profile for a Unit