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7 Replies Latest reply: Sep 2, 2013 10:41 PM by Aman.... RSS

Leaf nodes in Flex cluster

Sekar_BLUE4EVER Newbie
Currently Being Moderated


Hi,

  can somebody explain what leaf nodes in flex cluster are?from documentation I see that they are nodes which dont have access to storage and they communicate with hub nodes.

  Can they have oracle db instances?If so how is data transfered between hub and leaf nodes?Through interconnect?Doesn't it overload the interconnect?

 

Thanks

Sekar

  • 1. Re: Leaf nodes in Flex cluster
    sb92075 Guru
    Currently Being Moderated

    Sekar_BLUE4EVER wrote:

     


    Hi,

      can somebody explain what leaf nodes in flex cluster are?from documentation I see that they are nodes which dont have access to storage and they communicate with hub nodes.

      Can they have oracle db instances?If so how is data transfered between hub and leaf nodes?Through interconnect?Doesn't it overload the interconnect?

     

    Thanks

    Sekar

     

    Please post URL to this documentation so we all can read same as you.

     

     

    How do I ask a question on the forums?

    https://forums.oracle.com/message/9362002#9362002

  • 2. Re: Leaf nodes in Flex cluster
    Sekar_BLUE4EVER Newbie
    Currently Being Moderated

    Hi,

    Please find the URL

    Oracle Flex Clusters

  • 3. Re: Leaf nodes in Flex cluster
    Aman.... Oracle ACE
    Currently Being Moderated

    The whole mechanism of this "Hub and Spoke" architecture is to "decrease" the load from the interconnect traffic. In this new Flex cluster architecture, only Hub nodes are going to be directly attached to the storage and would be connected to the other nodes using an interconnect. Thus, this makes them similar to the node architecture that we have in pre 12.1 database releases as well. The new addition is the Leaf node part which are designed to run the minimal stack on them. Lead nodes won't be interconnected with each other using any private network but each Leaf node would be attached to its Hub node only. Any data, if required by Leaf nodes, would be accessed by its Hub node only from the storage. And yes, the leaf nodes can have a db isntance on them as well.Your assumption that this architecture would increase the network traffic is actually wrong as using this Hub-Spoke mechanism, its actually going tobe decreased.

     

    HTH

    Aman....

  • 4. Re: Leaf nodes in Flex cluster
    Sekar_BLUE4EVER Newbie
    Currently Being Moderated

    Thanks Aman...Still confused about this...Consider the following scenario

     

    |       H1       |<------->  |        H2         |   <------> |       H3        |

    |                   |              |                      |               |                    |

    | L1  L2  L3  |              | L1   L2   L3   |               | L1  L 2 L3   |

    | _________|              |___________|               |__________|

     

    H depicts the hub nodes and L depict the leaf nodes.Assume each Hub node has 3 leaf nodes attached to them.

     

    Suppose L1 connected to H1 needs a block and modifies it and after sometime L1 connected to H2 needs the same block then it must follow the same 2 way/3 way grant as in normal cache fusion right?

     

    Does this actually increase the number of hops since the leaf nodes are not directly connected?

     

    Do we have any control over the leaf node to hub node mapping or is it all automatically managed?

     

    Thanks

  • 5. Re: Leaf nodes in Flex cluster
    Aman.... Oracle ACE
    Currently Being Moderated

    Sekar_BLUE4EVER wrote:

     

    Thanks Aman...Still confused about this...Consider the following scenario

     

    |       H1       |<------->  |        H2         |   <------> |       H3        |

    |                   |              |                      |               |                    |

    | L1  L2  L3  |              | L1   L2   L3   |               | L1  L 2 L3   |

    | _________|              |___________|               |__________|

     

    H depicts the hub nodes and L depict the leaf nodes.Assume each Hub node has 3 leaf nodes attached to them.

     

    Suppose L1 connected to H1 needs a block and modifies it and after sometime L1 connected to H2 needs the same block then it must follow the same 2 way/3 way grant as in normal cache fusion right?

     

    Does this actually increase the number of hops since the leaf nodes are not directly connected?

     

    Do we have any control over the leaf node to hub node mapping or is it all automatically managed?

     

    Thanks

     

    The blocks are going to be accessed, modified at the Hub nodes only AFAIK as the Hub nodes are considered as DB Nodes. The Leaf Nodes are going to be considered as the Application Nodes. That's the reason, it's better to set up the instances running on the Hub Nodes only rather than the Leaf Nodes. Even if the instance runs on a Leaf Node, the communication is between the Hub and Leaf node only and it won't do any harm as both the nodes-Hub and Leaf(and the other nodes in the Leaf group) would be talking to each other directly. There is no VIP required on the Leaf Nodes so the connections by the database users would be only on the Hub Nodes, I guess and that means, the block movement would remain essentially the same.

     

    The number of network hops are reduced as you won't be having a requirement to have too many Hub Nodes since each Hub node can connect to  64(?) Leaf Nodes. So essentially, in your case, you would need only 4 Interconnects (2 on one Hub Node and 1 each on the remaining two) for the private interconnect and just 3 network links for the storage for each Hub node.

     

    I am not sure that I understood the last question of yours.

     

    HTH

    Aman....

  • 6. Re: Leaf nodes in Flex cluster
    Sekar_BLUE4EVER Newbie
    Currently Being Moderated

    Hi Aman,

        So does this mean the rac instances can be present only in HUB nodes?

        Or if the rac instances can be present in leaf nodes too(not sure if its possible since theydont have vip as you said) then the hub node has to coordinate the cache fusion on its behalf right/

        The last question what I meant was can we assign particular leaf nodes to a hub node or is it managed automatically?

     

    Thanks


  • 7. Re: Leaf nodes in Flex cluster
    Aman.... Oracle ACE
    Currently Being Moderated

    The RAC instances are supposed to be present on the Hub nodes as they are meant to be used as DB nodes . This would make the Cache Fusion concept similar to what we have in the previous releases. About the management of the nodes, you would need to assign explicitly, which nodes would be considered as  Leaf nodes out of the list of the total nodes available.

     

    HTH

    Aman....

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