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Windows Cluster Support in a SAN

In a SAN configuration, you can back up shared cluster resources to shared SAN devices, and failover to alternate paths when the primary path fails is supported. You should define SAN device paths for all physical nodes in a cluster; but not for the virtual node.

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The following rules apply to cluster support in a SAN:

  • All physical cluster nodes must have the same set of defined SAN devices.

  • The Device ID for any given SAN device must be identical on all cluster nodes.

To verify that the device paths are properly configured, use the Detect utility. Run detect from each physical cluster node. You must confirm that the same set of SAN devices are defined on each cluster node, and that the Device ID identifying each SAN device is the same for each node.

To use the Detect utility, go to the desired node and run the following from a command prompt:

detect -q

For example, if you had a cluster with two physical nodes that is part of a two tape drive SAN, run detect -q first on Node 1, then again on Node 2. The output might appear as follows:

Detect Output for Node 1:

SCSI Devices found:
------------------
Device       Adapter     Target            Device
File         ID      BUS ID     LUN STATUS Type                     String
------------ ------- --- ------ --- ------ ------------------------ ---------------------
\\.\Tape0    2       0   0      2   0      Sequential Access Device SONY       SDX-500C
\\.\Tape1    2       0   0      5   0      Sequential Access Device SONY       SDX-500C
\\.\sync_sa0 2       0   0      3   0      Media Changer Device     BHTi       216
\\.\Tape2    2       0   0      1   0      Sequential Access Device QUANTUM DLT8000
Device                    Serial / Unique                                    DPX
File                      Number / Id              World Wide Name           Auto
------------------------- ------------------------ ------------------------- ----
\\.\Tape0                 0000902585               20 0 0 50 13 b0 78 94     Yes
\\.\Tape1                 0000911832               20 0 0 50 13 b0 78 94     Yes
\\.\sync_sa0              216B10                                             Yes
\\.\Tape2                 PXB34P3669               20 0 0 50 13 b0 78 94     Yes

Detect Output for Node 2:

Confirm that both SAN Devices (Sony SDX-500C) are on both nodes. Use the Serial Number field to assure they are the same. Then confirm that the Device ID for each of the two SAN Devices is identical on Node 1 and Node 2. The Device ID is in the Device File field.

In this example, \\.\Tape0 is the Device ID for the drive whose serial number is 0000902585; and \\.\Tape1 is the Device ID for the drive whose serial number is 0000911832. This is true for both nodes, so you have a valid SAN setup for the cluster. ( \\.\Tape2 is a locally attached drive for Node 1. \\.\sync_sa0 is the media changer.)

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Note. Using a cluster node to control the media changer is not recommended.

If Detect shows that your SAN/cluster setup is not valid, reconfigure the paths between cluster nodes and SAN devices as needed.

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