Dell NetWorker 19.9 Administration Guide

Cloning operation logic for selecting a read source storage node

The cloning operation uses the following logic to determine the read source storage node:

1. If the source volume is mounted, then the storage node of the device on which the volume is mounted is used as the read source except in the following scenarios:

   • If the FORCE_REC_AFFINITY environment variable is set to Yes.
   • If the volume resides in a Virtual Tape Library (VTL) environment such as a CLARiiON Disk Library (CDL).

   In these scenarios, the NetWorker software ignores whether the source volume is mounted and behaves as though the volume is not mounted.

2. If the source volume is not mounted or the FORCE_REC_AFFINITY environment variable is set to Yes, then the NetWorker software creates a list of eligible storage nodes, based on the storage nodes that meet both of the following criteria:

   • The storage node is listed in the Recover storage nodes attribute of the Client resource for the NetWorker server.

     If there are no storage nodes in the list and the Autoselect storage node checkbox in the NetWorker server Client resource is clear, then the clone operation uses the value in the Storage Nodes attribute for the NetWorker server Client resource.

     If there are no storage nodes in the list and the Autoselect storage node checkbox in the NetWorker server Client resource is selected, then the clone operation uses autoselect logic to choose the storage node.

   • If the requested volume is in a media library, then the storage node is listed in the Read Hostname attribute for the Library resource is used.

     If the Read Hostname attribute for the Library resource is not set, then all storage nodes on which any device in the library is configured are added to the list of eligible storage nodes.

     NOTE:If the volume is not in a media library, then the list of storage nodes is based only on the criterion for storage node settings in the NetWorker server Client resource.

Example

Consider the following example for a volume that resides in a media library and is not mounted:

• The Recover storage nodes attribute in the NetWorker server Client resource lists the following storage nodes in order:

  • Storage node F
  • Storage node E
  • Storage node D

• The Read Hostname attribute for the Library resource is not set, but the following devices in the media library are configured with storage nodes:

  • Device A is configured on storage node D.
  • Device B is configured on storage node E.
  • Device C is configured on storage node B.

The list of eligible storage nodes is the intersection of the two previous lists (storage nodes E and D). The order in which the storage node is selected depends on the order of the storage nodes in the Recover storage node attribute list. In this example, storage node E is selected first as the read source storage node. If storage node E is not available, then storage node D is selected.

If no matching storage nodes are found in the intersecting list, then an error is written to the daemon log file that indicates that no matching devices are available for the operation. To correct the problem, ensure that at least one matching storage node appears in both lists.