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5 Replies Latest reply: Dec 30, 2011 12:06 PM by damorgan RSS

Exadata extended RAC

Florent Newbie
Currently Being Moderated
Hi,

could we exented RAC between 2 exadatas ?
In this case how manage Voting Disk ?

Thank a lot

Edited by: 905160 on 30 déc. 2011 03:06
  • 1. Re: Exadata extended RAC
    robinsc Explorer
    Currently Being Moderated
    Hi The ocr and vote will be in ASM. The ASM diskgroups will actually extend to all the cells across both Exadata machines and hence will be accessible to all servers on the same infiniband network.
    Thanks
  • 2. Re: Exadata extended RAC
    andy.colvin Oracle ACE
    Currently Being Moderated
    It is supported to interconnect Exadata half racks and larger using the included spine switch (the infiniband switch at the bottom of the rack). See appendix G of the latest Exadata Owner's Guide for more information. Basically, you would cable the Exadata racks together and build one large storage grid across the racks. This would create one large RAC cluster, with the 3 default diskgroups (DBFS_DG, DATA, RECO). OCR and voting files would be spread across ASM disks just as they are now.
  • 3. Re: Exadata extended RAC
    gsalem Explorer
    Currently Being Moderated
    There are several points to consider about such a configuration:
    1- Ib cables can go a 100m or so, so this is not really a stretch cluster, as in any decent data center, 100m apart means 2 rooms.
    2- If you setup such a system, you need to configure ASM failure groups yourself, in a way to have the data from the first system mirrored on cells on the second system.
    3- if you use normal redundancy, and you loose one rack, you'll end up with the second system having no redundancy at all, and you better rebalance right away to be on the safe side, this means keeping free space to be able to rebalance. If you can afford it, have 3 systems, with high redundancy, so that the los of one keeps the remaining part mirrored.
    4- if you do it with 2 machines, better have a 3rd voting on an NFS server somewhere, like you would do with any stretch cluster.

    That said, I do not like, nor advise such a setup at all. setting up a DG site for HA is far more easier, useful, robust, .....
  • 4. Re: Exadata extended RAC
    Florent Newbie
    Currently Being Moderated
    Thank a lot gsalem,

    In fact I think noboby have made this configuration at this moment.
    So it is too simple to say yes just plug the IB cable without considerate all the problem .

    Thank a lot
  • 5. Re: Exadata extended RAC
    damorgan Oracle ACE Director
    Currently Being Moderated
    I am on full agreement. Can you do it is a very different question from "should you do it?" I wouldn't. But then I wouldn't do it with less than 3 systems even without the stretch component.

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