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  • Latest Post - ‏2014-03-16T18:03:40Z by Mangesh Shirke
33 Posts

Pinned topic V7000 Flashcopy - when is target available?

‏2014-03-14T11:13:52Z | storwize v7000


I'm creating a number of flashcopy volumes on a V7000. These will be clones so will be detached once they are complete.

When the Flascopy Consistency Group is started are my target vdisk then available immediately for access by the host that will have the mappings to these target vdisks or do I need to wait until the cloning is completed it's entirety?


Section 5.3.2 Summary of FlashCopy indirection layer algorithm in the SVC and V7000 services red book kind of suggests I can use the target vdisks immediately. But if my is host writing to the target when the grain hasn't been copied from the source it says "Hold the write".


The source volumes currently have no other Flashcopy mappings. I will be creating these purely to create a single clone of each of the source vdisks. 





  • Mangesh Shirke
    Mangesh Shirke
    45 Posts

    Re: V7000 Flashcopy - when is target available?


    Hi Glenn,

    I am assuming that you don't have dependant flashcopies. Kindly find below answers for your queries.

    1) Yes. If you are using clone option then V7000 storage will automatically delete flashcopy relationship after background copy completion. By default it uses background copy rate 50 and cleaning rate 50.

    2) No you don't have to wait to complete background copy. Once you start flashcopy consistancy group you can immediately start using flashcopy target volumes. In case of V7000 storage, when you start flashcopy consistancy group ti creates pointer or you can say bitmaps with source volume. This bitmaps will get updated as per read/ write operation and background copy on both source and target volumes.
    When host writes data on target volume, it will be written on corrosponding block. It will not impact source volume. Whereas when read request comes on target volume, at that time it will read metadata/bitmaps and check that particular block has been copied on target volume or not. If it copied then it will read it from there and will reply back to host. In case if that block is not yet copied then by using flashcopy pointers/Bitmaps it will fetch that data from source vdisk internally.

    I hope this answers your query. Kindly feel free to contact if you need any further clarification.

    Apology for bad English :) .

    Mangesh Shirke