Procedure: Understanding volume dependencies

In the event that one component in a redundant pair is offline or powered off, here is a description of how host access to volumes is dependent on an enclosure or canister in the system.

The impact that a service procedure might have on host access to data can be understood by using the management GUI.

Log on to the management GUI. Go to Monitoring > System.
Using the dynamic graphic, right-click a canister or an enclosure and select Show Dependent Volumes. The page displays which volumes would be inaccessible if the component were to be taken offline or powered off.

If, during a maintenance procedure, the Show Dependent Volumes action indicates there are dependent volumes, you might choose to stop the procedure to investigate whether it is possible to reinstate the redundancy in the system, so that a procedure can be carried out without loss of access to data. An example would be to carry out procedures to ensure both canisters in the enclosure are online before carrying out another procedure that powers off the only online canister in the enclosure.