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2 Replies Latest reply: Feb 8, 2013 5:47 AM by Sebastian Solbach (DBA Community) RSS

Extended RAC asm host based mir

user11977218 Newbie
Currently Being Moderated
Please guide about requirements to SAN , on installing and implementing :

Oracle Extended RAC 11gR2 and host based mirorring by Oracle automatic storage Management (ASM) .
What is the Pros/Cos in such configuration ?

Thank's
  • 1. Re: Extended RAC asm host based mir
    Bjoern Rost Oracle ACE Director
    Currently Being Moderated
    One of the advantages of ASM in that scenario is that ASM mirroring supports "preferred mirror reads". ASM knows about which part of a mirror pair is at the local and which one is at the remote site and will read from the local LUN instead from the remote one to avoid the latency hit that would come with querying the other lun.
    It solves or improves one downside of an extended distance rac cluster but there are still other things to consider, like network latency, disk writes and more

    Bjoern
  • 2. Re: Extended RAC asm host based mir
    Sebastian Solbach (DBA Community) Guru
    Currently Being Moderated
    Hi,

    an interesting setup for HA, however:

    a.) Make sure your latency between the nodes is low. Otherwise the performance might suffer. It is also for that reason that normally you are restricted about the distance to around 5km for Ethernet and 50km for DWDM.
    b.) Extended Cluster is NOT DR: E.g. a corrupt block on one side will likely be mirrored to the other side as well. If you are looking for a disaster recovery solution, take Data Guard.

    Also see this whitepaper:
    http://www.oracle.com/technetwork/products/clustering/overview/extendedracversion11-435972.pdf

    Regards
    Sebastian

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