Symptoms

MS DPM, a data protection and recovery application offering tape-based backups among others, poses an issue when working with tape libraries. The issue occurs on a random basis and leads to the separation of tape libraries into standalone tape drives. The tape library, in this case, is displayed in the DPM console as offline and can’t be connected to.

Resolution

To solve this issue, MS DPM provides a specific method for assigning tape drive LUNs to libraries.

The tape drive and library information are contained in a DPMLA.xml configuration file located within the configuration folder under the DPM server installation.

Currently, the tape library can be brought back online in one of the following ways:

  1. By manually creating the DPMLA.xml file from the LADriveRemappingTemplate.xml located in the configuration catalog of the DPM server installation
  2. By using the DPMDriveMapping.exe executable located in the bin catalog of the DPM server installation

The most straightforward way is to use the DPMDriveMapping.exe executable since it will create a new DPMLA.xml file. Here are the steps to follow:

  1. Open an elevated command prompt
  2. Run the DPMDriveMapping.exe from \Bin folder
  3. Start the DPM console
  4. Navigate to Management and libraries
  5. Run a Rescan

NOTE: Ensure the following before running the DPMDriveMapping.exe:

  • DPMLA service is not running
  • There no tapes in the drive
  • There is at least one tape in each library which is not marked as Cleaner

Additional information can be found in the Microsoft article at the following link:
https://technet.microsoft.com/en-us/library/bb795782.aspx
Since Microsoft iSCSI Initiator assigns Target|Bus|Lun to the targets in their appearance order by default, you may need to run the above-mentioned tape drive LUNs assignment procedure one more time when altering the target configuration.
In case of complex target configuration on the client host, there is an option to statically assign a target to Windows Target|Bus|Lun. For this purpose, run the following command:

AddTarget <TargetName> <TargetAlias> <TargetPortalAddress> <TargetPortalSocket> <Target flags> <Persist> <Login Flags> <Header Digest> <Data Digest> <Max Connections> <DefaultTime2Wait> <DefaultTime2Retain> <Username> <Password> <AuthType> <Mapping Count> <Target Lun> <OS Bus> <Os Target> <OS Lun>

Where:

  • TargetName is the name of the target.
  • TargetAlias is the alias for the target.
  • TargetPortalAddress is the IP or DNS address of the target portal.
  • TargetPortalSocket is the target portal TCP port number (commonly assigned as 3260).
  • Target Flags specify the flags that determine how the target is managed by the iSCSI initiator service.
  • Persist indicates if the target should be persisted and available after the service restart. By specifying T or t, the target is persisted. If no value is set, the target remains not persisted.
  • Login Flags is a set of flags that determine the behavior of iSCSI login to the target portal.
  • Header Digest is a non-zero value indicating that the initiator should enable header digest when logging into the target portal.
  • Data Digest is a non-zero value indicating that the initiator should enable data digest when logging into the target portal.
  • Maximum Connections specifies the maximum connections number for the discovery session to use when performing the SendTargets operation.
  • DefaultTime2Wait is the value used by the initiator to negotiate when logging into the target.
  • DefaultTime2Retain is the value used by the initiator to negotiate when logging into the target.
  • Username is the string used as the CHAP username when logging into the target. By specifying * for this parameter, the iSCSI initiator service will use the initiator node name as the CHAP username.
  • Password is the string used as the target’s CHAP secret when logging into the target. The initiator will use this secret to compute a hash value based on the challenge sent by the target.
  • AuthType is the type of authentication used when logging into the target.
  • MappingCount specifies the count of target mappings used by the initiator to login to the target.
  • Target Lun is the LUN value the target uses to expose the LUN.
  • OS Bus is the bus number that the operating system uses to surface the LUN
  • OS Target is the target number that the OS useses to surface the LUN
  • OS LUN is the LUN number that the OS uses to surface the LUN

More detailed information on assigning static targets can be found in the Microsoft iSCSI Software Initiator User Guide at the following link: https://download.microsoft.com/download/A/E/9/AE91DEA1-66D9-417C-ADE4-92D824B871AF/uGuide.doc

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