Intel® Virtual RAID on CPU (Intel® VROC) RAID Write Hole (RWH) Closure in Windows* Environments

Intel® Virtual RAID on CPU (Intel® VROC) can protect RAID 5 data even when both unexpected power loss and RAID volume degradation occur at the same time. This double fault condition is referred to as RAID Write Hole (RWH). Intel® VROC supports the ability to close the RWH scenario in RAID 5 configurations using a feature called RWH Closure. This applies to Intel® VROC enabled platforms.

Intel® VROC for Windows* supports the option to configure Partial Parity Logging (PPL) from the Intel® VROC Graphical User Interface (GUI) application while the system is running, without requiring a platform reboot. This feature is disabled by default.

Marking a Drive as a Journaling Drive

A drive can be marked as a journaling drive, in order to close the RWH on a RAID 5 volume. Such drive is no longer available in the system and cannot be used for any other purpose. The Journaling Drive method of closing the RWH typically provides better performance compared to the Distributed method.

Mark Drive as a Journaling Drive During a Volume Creation

1. Open the Intel® VROC GUI application.
2. Click the Create Volume option.
3. Select the controller.
4. Select the option for RAID 5.
5. Click Next.
6. Select the required number of drives.
7. Click Next.
8. On the Configure page, select the Journaling Drive mode for RAID Write Hole Closure.
9. Select the drive to mark as a journaling drive.
10. Click Next. This button will not be active until all the required selections have been made.

Mark Drive as a Journaling Drive on an Existing Volume

1. Open the Intel® VROC GUI application.
2. Navigate to the volume on which an action should be performed.
3. Click the Actions option from the management section, and a side menu will open.
4. Click the Change RAID Write Hole Closure mode option from the side menu.
5. Select the Journaling Drive option.
6. Select the drive to mark as a journaling drive.
7. Click OK to confirm.

RWH Recovery

The Intel® VROC driver for Windows* enters into an RWH recovery state when a RAID 5 volume encounters an RWH failure condition. There are two levels of this RWH recovery process. The first level is the recovery after a dirty shutdown. In this case, the recovery process goes through the intent log (PPL) to make the RAID volume consistent for in-flight stripes that might be inconsistent. The second level recovery is when a dirty shutdown is followed by a drive failure. In this case, the recovery process references the intent log (PPL) to first make things consistent despite a member drive not being present.

The RWH recovery process will resume if the system is shut down or restarted.

During an RWH recovery process:

• RAID volume rebuild is disabled. Once the recovery is complete and the RAID 5 data is consistent, then we can begin the rebuild process.
• The Verify and Repair option on a dirty shutdown is disabled. The Verify and Repair process is covered by the RWH recovery process.