With the Validate a Configuration Wizard, you can run tests to confirm that your hardware and hardware settings are compatible with failover clustering. You can run the complete set of configuration tests or a subset of the tests. Microsoft recommends that you run the tests on your set of servers and storage devices before you configure them as a failover cluster (create a cluster from them). You can also run the tests after you create a cluster.
Note: The Failover Clustering feature must be installed on all the servers that you want to include in the tests.
Microsoft supports a failover cluster solution only if the complete configuration (servers, network, and storage) can pass all tests in the Validate a Configuration Wizard. Because improvements in failover clusters require that the storage respond correctly to specific SCSI commands, the storage must follow the SCSI Primary Commands-3 (SPC-3) standard. In particular, the storage must support Persistent Reservations as specified in the SPC-3 standard.
- What is a “Logical Unit Number” (LUN)? A logical unit number, or LUN, is a number used to identify a logical unit, which is a device addressed by the SCSI protocol or Storage Area Network (SAN) protocols which encapsulate SCSI, such as Fibre Channel or iSCSI.
- What is a “Persistent Reservation” (PR)? A PR is a SCSI command which clustering uses to protect a LUN.
When a LUN is reserved, no other computers besides the cluster nodes on the SAN can access the disk. In other words, the SCSI-3 PR command prevents other machines from accessing the disk and corrupting the data on the disk.
The “Validate SCSI-3 Persistent Reservation” test ensures that the cluster storage uses the more recent (SCSI-3 standard) Persistent Reserve commands (which are different from the older SCSI-2 standard reserve/release commands). The Persistent Reserve commands avoid SCSI bus resets, which means they are much less disruptive than the older reserve/release commands. Therefore, a failover cluster can be more responsive in a variety of situations, as compared to a cluster running an earlier version of the operating system. In addition, disks are never left in an unprotected state, which lowers the risk of volume corruption.
When running the Cluster Validation Wizard in Windows Server 2008, 2008 R2, 2012, 2012 R2, with a LUN presented by the HP EVA Storage Array to your cluster nodes, the SCSI-3 Persistent Reservation test may fail with an error such as the following:
Validate SCSI-3 Persistent Reservation Validate that storage supports the SCSI-3 Persistent Reservation commands. Validating Cluster Disk 0 for Persistent Reservation support Registering PR key for cluster disk 0 from node node1.cluster.com Failed to Register PR key for cluster disk 0 from node node1.cluster.com status 1 Cluster Disk 0 does not support Persistent Reservation
- If the wrong Host Operating System connection type is configured on the HP EVA, you cannot share the disks between the cluster nodes and the cluster check will fail with a non-SCSI-3 compliant message.
- If the firmware on the HP Storage Array is not updated to support Windows Server 2008, 2008 R2, 2012, or 2012 R2, you will not see the Operating System type available in the drop-down list.
As a result, you must add the following custom code.
- Within HP Command View, expand the folders under the HP EVA Storage array.
- Expand the “Hosts” folder.
- Click on the cluster node host.
- Under “Host Properties” on the “General” tab, under the “Operating System” section, in the “Type:” field, choose “Custom” on the drop-down list.
- In the “Custom Type:” field, type the following HEX number: 00000004198009A8.
- Repeat these steps for all your cluster node hosts.