ShadowSnap's Interaction with iSCSI volumes

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Scope

This article discusses the interaction between the ShadowSnap agent with the iSCSI volumes.

Resources

Below are resources about the Microsoft iSCSI Software and how it works:

Interaction with the iSCSI Volumes and the ShadowSnap Agent

iSCSI volumes are useful solutions for expanding storage and allowing multiple machines to interact with a single storage volume. Due to their typically dynamically expanding nature, iSCSI volumes in dynamic configurations will contract and expand as required. This causes issues when ShadowSnap goes to take a backup of the agents: If the volume has expanded, ShadowSnap must create a new sparse image.

iSCSI is also used by the Datto solution to perform file restores where the original security permissions must be retained by the restore.

Even a consistently shrinking volume may run into issues when being protected by the Datto appliance. Since ShadowSnap's operation is to determine the disk configuration from Windows, it will attempt to back up drives that appear as local volumes. Differential merges will on the volumes as they change their configurations.

When backing up an iSCSI volume, if the session state gets disconnected, this can cause the volume state to activate a new session ID.

This will cause a differential merge as the incremental tracking state is reset. It potentially can cause an error as such:

   -N6:
        -initiator: Session state timeout occurred, or a session
            reinstatement cleared this session instance.  This results
            in the freeing of all associated resources and the session
            state is discarded.
        -target: Session state timeout occurred, or a session
            reinstatement cleared this session instance.  This results
            in the freeing of all associated resources and the session
            state is discarded.

Microsoft iSCSI Updates

  • Microsoft has two locations for iSCSI specific software packages. Ensure that the latest versions are always being used upon setup and configuration.
  • When setting up volumes for backup, make sure the volumes appear as locally accessible volumes on the target server and once configured, will not be manipulated.
  • Configurations of these volumes are beyond the scope of Datto Technical Support.

Additional Resources


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