SRDF/Metro online device expansion

With the new PowerMaxOS 5978.444.444 release, you can now expand SRDF/Metro devices, and thus the VMware datastores built on top of them, online. You may recall in our current release you can expand SRDF/Metro devices but it does require suspending access to the R2 by changing the RDF mode to synchronous. I wrote this up previously here. In the new release it works the same as it does for the other SRDF modes. I’ve done a quick example with the screenshots below.

In this example I’m using a 25 GB device replicating with SRDF/Metro. I’ve employed a virtual witness so the pair is in an ActiveActive state.

I presented this device to a vMSC cluster and created a datastore called SRDF_METRO_EXPAND on it.


Now I wish to expand the datastore to 100 GB. I’ll start in Unisphere for PowerMax to first expand the underlying device. I can navigate to either the R1 or the R2 to expand, this is true whether or not the state is ActiveActive or ActiveBias. In this case I am going to start at the R1, which is device 00037 on array 358, and click on Expand. This will start the wizard for expansion (step 2) which is the same for all RDF types. Using the drop-down box select the RDF group in step 3 and set the volume capacity in step 4 before running the job. The array will expand both 00037 and its pair 0010E on array 357 in step 5.

Once expanded, the device is now at 100 GB.


I can now finish the process by increasing the datastore extent in vSphere from 25 GB to 100 GB. The three steps of the wizard are shown below. If you have issues with the wizard discovering the newly expanded device, login directly to one of the ESXi hosts through the GUI. I’ve noted the bug in VMware where sometimes vCenter does not properly show the device for expansion.


This completes the expansion, all done online.


If you have an SRDF/Metro setup with an asynchronous leg off one side or both, you cannot do the entire process online. Fortunately the SRDF/Metro site will remain online, but the remote leg(s) requires suspension. Basically you suspend and expand the async device(s), then expand the SRDF/Metro pair. This is covered in the docs.

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