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Considerations & Limitations for Shared Advanced File Type Device (AFTD)

March 7, 2012

In a Network Attached Storage (NAS) environment, NetWorker operations can be performed concurrently on two storage nodes that share an AFTD. When sharing an AFTD, one storage node can save to a writable volume, while the other storage node either recovers or clones from a read-only volume.

In a Storage Area Network (SAN), NetWorker operations are performed sequentially when two storage nodes share an AFTD. Only one storage node at a time can use the shared AFTD.

So you have to check the following considerations and limitations before implementing this Shared AFTD device:

Shared AFTD considerations:

Review these considerations before sharing AFTDs:

  • Ensure that operating system permissions (directory and file) and sharing are set up properly between storage node hosts for the root user or Windows administrator, to enable proper sharing of AFTDs on the file system.
  •  Use operating system commands to create, copy, or erase directories or files on the sharing disk (such as NAS, JBOD in SAN), to ensure that sharing is possible at file system level between machines. If the operating system does not permit such sharing, then the NetWorker software cannot change that.
  •  To share an AFTD between storage nodes, ensure to:
    • Set the proper Storage Node and Clone Storage Node attributes in the Client resource.
    • Specify for the Staging resource, the proper Device attribute (the one with the read-only volume mounted).
  • To share an AFTD in NAS on Windows storage nodes, ensure to:
    • Start the nsrexecd (NetWorker Remote Exec) service is started by a Windows Administrator account on the storage node.
    • Create the CIFS-mapped AFTD with UNC pathnames that have the appropriate remote user and password specified. An example of UNC path syntax is:   rd=sn_a:\\nas1\path\shared_aftd

Shared AFTD limitations

Shared AFTDs include these limitations:

  • Read-only volumes might be auto-mounted onto the writing storage node during saves. The workaround is to un-mount all sharing instances of read-only and read-write AFTD volumes from all storage nodes, and then correctly remount them.
  •  Limitations on sharing AFTD between storage nodes in NAS/SAN:
    • Supports only homogeneous storage node platforms when sharing AFTD (such as Windows with Windows storage nodes, or UNIX with UNIX storage nodes).
  • The sharing read-write or read-only AFTD volume must be manually un-mounted from one storage node before being mounted on another, in order to prevent a potential out-of-sync state for the volume.
  •  All instances of the sharing read-write or read-only AFTD volume must be manually un-mounted from all of the sharing storage nodes before relabeling the sharing AFTD, in order to prevent potential data loss.

For SAN only:

  • One storage node at a time can perform NetWorker operations.
  • Use operating system or SAN commands to mount or enable the sharing disk on the second storage node after un-mounting or disabling from the first storage node. This ensures that file and directory sharing of the same disk is supported (set up) in the SAN from the sharing storage nodes, allowing the sequential sharing of the disk as an AFTD in the NetWorker software.
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