Procedure: Understanding Storwize V7000 Gen2 volume dependencies
If one component in a redundant pair is offline or powered off, host access to volumes depends on a Storwize® V7000 Gen2 enclosure or canister in the system.
- If a control enclosure only has one node canister online, access to a volume depends on the online node canister if the volume is stored partially or wholly on an array that uses drives in the control enclosure or its expansion enclosures.
- If one expansion canister in an expansion enclosure is powered off, any expansion canisters further down that side of the chain become isolated from the control canister on that side of the chain. In this case, host access to volumes depends on the online canister if the volume uses drives in an isolated enclosure or the enclosure with the offline canister.
- If an entire expansion enclosure is powered off, both the left and the right side of the SAS chain are broken. In this case, host access to some volumes can be considered to depend on the entire expansion enclosure.
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 .
- From the dynamic graphic, right click the canister and select Show Dependent Volumes to see which volumes would be inaccessible if the component was taken offline or powered off.
If during a maintenance procedure, the Show Dependent Volumes action indicates that 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 do procedures to ensure that both canisters in the enclosure are online before doing another procedure that powers off the only online canister in the enclosure.