Topic
7 replies Latest Post - ‏2014-03-29T14:58:01Z by Mangesh Shirke
TMasteen
TMasteen
280 Posts
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Pinned topic SVC behind SVC

‏2014-03-28T15:28:20Z |

Hi all,

We know we can put a V7000 behind a SVC. The V7k behind SVC  has: layer = storage.

The default setting in the SVC is: layer = replication.

But suppose I want to put a SVC (A) on top of a SVC (B,  wich has external storage), should it be possible to provide Vdisks from SVC B to SVC A?

SVC B has no partnerships.

  • Mangesh Shirke
    Mangesh Shirke
    43 Posts
    ACCEPTED ANSWER

    Re: SVC behind SVC

    ‏2014-03-28T18:03:41Z  in response to TMasteen

    Hi,

    Logically speaking yes you can virtualize SVC behind SVC. But I don't understand why do you have requirement to virtualise SVC behind SVC. You question is quiet interesting and I would like to get more details about it.

    Firstly I would like to know why and what is exact requirement for this configuration. Normally we virtualise storage for below reasons.

    1) To get more cache.

    2) To get more backend spindles.

    3) To manage multiple storages under one tree and optimize resources.

    But in this case as we are virtualizing SVC behind SVC none of this purpose is full filled. Yes I do agree that we are adding one more cache layer in system. But is it really a requirement....??? Because doing this will add one additional hope to fetch data from disks.

    If possible kindly share you requirement for which you are thinking of this configurations.

     

    Coming back to your question. Logically yes we can virtualize SVC behind SVC. But officially it is not supported by IBM. Kindly refer below link for compatibility list for SVC.

    http://www-01.ibm.com/support/docview.wss?uid=ssg1S1004392#_Drive

    You can also get detailed compatibility details on below link.

    http://www-03.ibm.com/systems/support/storage/ssic/interoperability.wss

     

    Thanks.

    Mangesh Shirke

    • TMasteen
      TMasteen
      280 Posts
      ACCEPTED ANSWER

      Re: SVC behind SVC

      ‏2014-03-28T19:24:33Z  in response to Mangesh Shirke

      Mangesh,

      Suppose you have a migration service which can be done by SVC. Now you want to migrate a datacenter with a SVC environment but that Datacenter has no replication licenses. Suppose we do have SVC clusters with replication licenses.. So now we want to "import" the vdisks coming from the DC as image mode vdisks in our SVC and replicate them to another datacenter.

      I know it's not on a support matrix, but I can think of more scenario's which are not on the list...

      • Mangesh Shirke
        Mangesh Shirke
        43 Posts
        ACCEPTED ANSWER

        Re: SVC behind SVC

        ‏2014-03-29T14:58:01Z  in response to TMasteen

        Hi,

        Can you please give more clarity on this query...??

        Thanks.

        Mangesh Shirke

  • chriscanto
    chriscanto
    276 Posts
    ACCEPTED ANSWER

    Re: SVC behind SVC

    ‏2014-03-28T19:39:13Z  in response to TMasteen

    Hi TMasteen,

    I'm afraid Mangesh's response is incorrect.  It is not possible to virtualize one SVC with another SVC.  This is because they are in the same system 'layer' (and cannot currently be changed), and so see each other as peers for remote copy (i.e. Metro/Global Mirror), rather than as an external storage system.

    There's some good information on the topic of system layers in the Information Center:

    http://pic.dhe.ibm.com/infocenter/svc/ic/topic/com.ibm.storage.svc.console.720.doc/svc_systemlayer.html

     

    Hope that helps,

    Chris

    • TMasteen
      TMasteen
      280 Posts
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      Re: SVC behind SVC

      ‏2014-03-28T20:22:46Z  in response to chriscanto

      Hello Chris,

      Thank you for your reply.

      Still wondering what will happen if I define the "Top\Upper" SVC as a host in the "Bottom\Lower" SVC like we do in any other storage array?  I have tested a vplex in front of a SVC without problems.

      • chriscanto
        chriscanto
        276 Posts
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        Re: SVC behind SVC

        ‏2014-03-28T21:14:07Z  in response to TMasteen

        The node ports for the "bottom" SVC system you're attempting to virtualize wouldn't appear as controller ports on the "top" one, likewise the ports on the "top" SVC system won't appear to the other as host port candidates for you to create a host object with.

        This behaviour is intentional, applied in the SVC software, but it could be changed -- if there was a compelling use-case then you should definitely think about submitting a Request For Enhancement (RFE):

        http://www.ibm.com/developerworks/rfe

         

        It's different to having another a virtualisation device in front of the SVC, where the approach you describe will work, because SVC recognises the remote nodes as another SVC and treats it in a special way, allowing for things like clustering and remote copy.

         

    • Mangesh Shirke
      Mangesh Shirke
      43 Posts
      ACCEPTED ANSWER

      Re: SVC behind SVC

      ‏2014-03-29T14:54:36Z  in response to chriscanto

      Hi Chris,

      Thanks for correction. Yes you are right. SVC is in replication layer by default and currently we do not have option to change it.

      In past while doing testing on SVC I was virtualized SVC behing SVC. But that was only for testing purpose. And no data or LUN migration was performed. I was added WWPN manually.

      As I mentioned in my earlier comment this is not supported. And if any how we configure it then we don't know how it will repond and how will it work.

      I will go with your reply. We can not really virtualize SVC behind SVC.

      Thanks.
      Mangesh Shirke