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Using ATF_RESTORE to move LUNs back to the default Storage Processor - Technical Tip - 149588




How to Tell that a TRESPASS has occurred.

In PowerVault 650F installation that includes redundant data paths it is possible to communicate to the 650F through one or both data paths. A data path is defined as One HBA (Qlogic) connected to one Storage Processor (SP). The data path may also include Fibre channel Switches (50F & 51F). Within the 650F LUNs are assigned to specific Storage Processors and therefore to specific data paths. If a data path becomes invalid then it may be possible to restore access to the effected LUNs by reassigning them to the other Storage Processor and data path. The Application Transparent Failover (ATF) program is responsible for automatically reassigning LUNs when a data path fails. When this happens it is called a TRESPASS. Only LUNs that are effected will be trespassed. For example if we have a SAN with Server_1 and Server_2 both are connected to a single 650F with four LUNs. StorageC is installed. See chart for configuration.

LUN1

Storage Processor A

Assigned to Server_1

LUN2

Storage Processor B

Assigned to Server_1

LUN3

Storage Processor A

Assigned to Server_2

LUN4

Storage Processor B

Assigned to Server_2

If the data path from Server_1 to Storage Processor B fails then StorageC would Trespass LUN2 from SPB to SPA. It would NOT Trespass LUN4 that is also on SPB because the data path from SPB to Server_2 is intact.

How to Tell that a TRESPASS has occurred

There are three ways to tell that a trespass has occurred.

    1. ATF will leave one or more messages in the NT System Event log
    2. ATF will leave one or more messages in the Unsolicited Event Logs (Ulogs)
    3. The "Default SP" property of a LUN is different from the SP that it is currently assigned to.

How to Move LUNs back to the default SP

    1. Verify that the data path problem that originally caused the trespass has been resolved.
    2. Open a Command prompt on any server with a Fibre channel connection to the 650F and ATF is installed..
    3. Change directories to "Program Files\Dell OpenManage\Powervault Manager\Dell Openmanage ATF"
    4. Execute the following command : "ATF_RESTORE ATF_SP0"
    5. Use the OpenManage Data Supervisor or Administrator to verify that the restore took place. It might be necessary to request a Manual Poll of the 650F in order to update the application.

Additional Information

The "ATF_RESTORE ATF_SP0" command will inspect every LUN in the 650F and move any LUN that is not currently assigned to it’s "Default SP".

It is possible to permanently change the SP that a LUN is assigned to by first changing the Default SP assignment for the LUN and the executing the ATF_RESTORE ATF_SP0 command to then move the LUN to it’s default SP.



Background Information on ATF_Restore

In PowerVault 650F installation that includes redundant data paths it is possible to communicate to the 650F through one or both data paths. A data path is defined as One HBA (Qlogic) connected to one Storage Processor (SP). The data path may also include Fibre channel Switches (50F & 51F). Within the 650F LUNs are assigned to specific Storage Processors and therefore to specific data paths. If a data path becomes invalid then it may be possible to restore access to the effected LUNs by reassigning them to the other Storage Processor and data path. The Application Transparent Failover (ATF) program is responsible for automatically reassigning LUNs when a data path fails. When this happens it is called a TRESPASS. Only LUNs that are effected will be trespassed. For example if we have a SAN with Server_1 and Server_2 both are connected to a single 650F with four LUNs. StorageC is installed. See chart for configuration.

LUN1

Storage Processor A

Assigned to Server_1

LUN2

Storage Processor B

Assigned to Server_1

LUN3

Storage Processor A

Assigned to Server_2

LUN4

Storage Processor B

Assigned to Server_2

If the data path from Server_1 to Storage Processor B fails then StorageC would Trespass LUN2 from SPB to SPA. It would NOT Trespass LUN4 that is also on SPB because the data path from SPB to Server_2 is intact.



 
Quick Tips content is self-published by the Dell Support Professionals who resolve issues daily. In order to achieve a speedy publication, Quick Tips may represent only partial solutions or work-arounds that are still in development or pending further proof of successfully resolving an issue. As such Quick Tips have not been reviewed, validated or approved by Dell and should be used with appropriate caution. Dell shall not be liable for any loss, including but not limited to loss of data, loss of profit or loss of revenue, which customers may incur by following any procedure or advice set out in the Quick Tips.

ID do artigo: SLN67135

Data da última modificação: 07/29/2010 12:00 AM


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