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Exadata as a host for vDBs

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  • 1.  Exadata as a host for vDBs

    Posted 11-03-2020 02:25:00 AM
    Hi Team,

    We have a setup in which we have an ODA as a target host to create the vDBs. The sources are diverse in terms of ODAs and Exadatas.

    One of our Source DBs is huge, in the sense that the table not only has rows in the magnitude of billions but also columns in the order of hundreds. While normal DML operations on the vDB created from this source on ODA works well, there is in general an issue with performance of large joins or simple where clauses on large tables.

    In my view, this is expected, on the source side the DB runs on EXA and uses the capabilities such as offloading and smart scan, but since the vDB is on ODA, these capabilities are missed and hence the slower performance.

    Question : If the target host was also EXA, as in vDB would run on EXA, will the vDB still be able to use some of the features specific to EXA platform even though with the vDB we will not be using Oracle provided storage ?


  • 2.  RE: Exadata as a host for vDBs

    Posted 11-03-2020 02:48:00 AM

    Hello Mayank,

    Thanks for using the forum to reach out.
    The following article may help answer your questions.

    Deploying Delphix with Exadata

    Please let us know if you have further questions.
    Best regards.



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    Luke Moss
    Delphix Support
    Delphix
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  • 3.  RE: Exadata as a host for vDBs

    Posted 11-03-2020 05:04:00 AM
    Edited by Mouhssine SAIDI 11-03-2020 12:12:46 PM
    Hi Mayank,

    Th short answer to your question is no, Vdb can't benefit from exadata storage features because disks holding data aren't under exadata storage. Unless you are using a storage brand from oracle like pillar or ZFSSA for holding your delphix disks.

    But to help give some boost to your VDBs under ODA, can you please give more details on your configuration :

    1/ Can you give a blueprint on the actual architecture ?
    2/ CPU and Memory reservation are in place for the engine ?
    3/ Database version involved ?
    4/ Are you using Dnfs instead of nfs to access delphix disks ?
    5/ How many hops do you have between your delphix engine and targeted ODA ?
    6/ Is there any FW ?
    7/ Vdb's parameter are inherited from the source one ?

    You can also check the following links regarding VDB performance
    https://support.delphix.com/Delphix_Virtualization_Engine/Delphix_Admin/FAQ%3A_Virtual_Database_(VDB)_Performance_(KBA1247)
    https://support.delphix.com/Delphix_Virtualization_Engine/Oracle/Troubleshooting_Oracle_VDB_Performance_-_View_Performance_Analytics_(KBA1335)
    https://support.delphix.com/Delphix_Virtualization_Engine/Oracle/Troubleshooting_Oracle_VDB_Performance_(KBA1412)
    https://support.delphix.com/Delphix_Virtualization_Engine/Oracle/Troubleshooting_Oracle_VDB_Performance_-_Display_and_Set_NFS_Kernel_Parameters_(KBA1500)
    https://docs.delphix.com/docs53/architecture-best-practices/architecture-best-practices-for-target-db-and-os-settings


    KR,

    Mouhssine

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    Mouhssine SAIDI
    Community Member
    Delphix Community Members
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  • 4.  RE: Exadata as a host for vDBs
    Best Answer

    Posted 11-03-2020 10:09:00 AM
    1)  Mouhssine is correct, the storage is underneath the Delphix Engine, the Exadata machine is only being used for compute (CPU and RAM).  Smartscan will not be available.
    2)  You might consider adding indices (indexes) to the tables, especially if you're seeing that it's slow for "simple where clauses on large tables".  Indices are routinely deleted when using Exadata, but you can add them back as part of a Delphix Hook.  Adding an index on a large table can be slow, so consider doing this just once to create a "gold copy" VDB which you then clone and distribute to users.  (The "gold copy" can also be transformed in other useful ways:  prune/subset, add test data, mask, etc).

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    Ranzo Taylor
    Technical Services Director
    Delphix
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  • 5.  RE: Exadata as a host for vDBs

    Posted 11-04-2020 01:30:00 AM
    Thanks guys ! This was my understanding as well, still wanted to check.

    As for the architecture, we have the Delphix engine and the target host in the same subnet, so no FW, no hops between. We also use Direct NFS and the oracle version is 12.1.

    As for initialization parameters on the vDB, I don't inherit them from the source, instead i give larger SGA, dedicated larger buffer cache etc.

    In general the architecture performs very well, the issue just is with this one application, since this has tables that have a blueprint of 0.5 TB on disk. Even without vDBs, this specific system has the same performance issues on ODA, and hence the hopeful question :)


    Regards,
    Mayank


  • 6.  RE: Exadata as a host for vDBs

    Posted 11-09-2020 03:02:00 AM
    Hi Mayank,

    Happy to hear that this isn't a side effect of using database virtualization and that you face the same issue on ODA.

    Genereally speaking exadata dont need non-anamytical indexes implementation (this is one of oracle's exadata best practicies), so as Taylor suggested you can look for adding necessary indexes as part of configure clone hooks to the VDBs you're creating on ODA.

    If this didn't help match, just go with the classical tunning path of a database as you will do for physical ones.

    Regards,

    Mouhssine

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    Mouhssine SAIDI
    Community Member
    Delphix Community Members
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