VNX – Creating cascaded clones, sort of..

If you are familiar with VMAX TimeFinder/Clone you will easily recognized what this is,  TimeFinder/Clone Cascaded clone feature.  There are a lot of use-cases that would allow one to take advantage of this feature, one example would be to refresh a dev or test environment from a nightly clone of production.

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Great feature but what if you need to do same thing on a VNX ?  Unfortunately native Snapview Clone software will not allow you to create clone of “C” because clone “B” is a target of another clone session. If you try to create a clone session by selecting B as your source (regardless if it’s synchronized or fractured)  you will get an error message similar to this:

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So what do we ?  Well we reach out to our good ol’  friend SANCopy.  Most people know and use SANCopy for array to array migration but not many know that you can also use it for intra array copies.  Typically intra array copies are performed using SnapView clone but this is a special case.  SANCopy will allow us to create a completely new session between  “B” and “C”.   Here is how :



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First step we create a standard SnapView Clone session between LUN Oracle_A and Oracle_B and

then Fracture it.

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Next step we are going to create a SANCopy session between LUN Oracle_B and Oracle_C.

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Here is one caveat,  as you can see from the screenshot below we do not see LUN ID 12000 which should be our Oracle_C. We don’t see it because our source LUN (Oracle_B) is currently owned by SPB and our target (Oracle_C) is owned by SPA. So we need to trespass  Oracle_C to match SP owner of source LUN, SPB in this case.

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Once you trespass the target LUN, you will see it in the destination list and you can go ahead and create the session. Once session is created we need to start it, in Unisphere navigate to Storage > Data Migration > Sessions Tab.  Select the session and hit Start8-16-2014 9-28-59 PM

Now if you select the SAN Copy LUNs tab you will see this, i know it looks as if we have two different sessions, don’t worry it’s normal.

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When session Status changes to Completed you can go ahead and delete the SANCopy session. SANCopy session can remain in place and will not impact your existing SnapView clone session between Oracle_A and Oracle_B. You can freely synchronize it and fracture it again. Finally if you had to trespass target LUNs , don’t forget to trespass them back after you delete the SANCopy session.