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Extended RAC and N-Way streams Replication

Oracle 作者:watershed 时间:2017-05-04 11:27:16 0 删除 编辑

今日在DBA-Oracle上看到一篇问答,很有意思,故转载以记录

Question:  What are the best options for a geographically distributed disaster recovery using RAC?  Can I use Data Guard or Streams for disaster recovery?


Answer: Yes, you can always use Streams or Data Guard for Disaster recovery, but if you have a distance of less than 90 miles, you can use a geographically distributed RAC cluster.


For distributed RAC you need a super-fast interconnect (e.g. "dark fiber" fiber channel connectivity) you can have geographically distributed RAC nodes, but a more common alternative to extended RAC is to use Data Guard or Streams (n-way replication) for disaster recovery. 


For shops with high capital funding (lotsa cash), you can employ Dense Wavelength Division Multiplexing (DWDM) technology or dark fiber, but it becomes very expensive over long geographical distances.


The choice depends mostly on costs and the volume of updates (DML) for the RAC cluster, plus your tolerance for unplanned outages during a disaster.  For enough money, you can guarantee continuous availability with extended RAC clusters, but if you can afford a 30 minute downtime, Data Guard or n-way Streams may be a better approach



Oracle n-way Streams replication

Oracle Database Tips by Burleson Consulting

February 9, 2015

Question:  What is Oracle n-way Streams replication?  I hear that n-way Streams replication is a faster failover alternative to Data Guard, but I see nothing in the Oracle documentation on n-way Streams.  How does n-way Streams replication work?

Answer:  You are correct, you will not find n-way Streams mentioned in the Oracle documentation because it is a specialized techniques that combines high availability with disaster recovery, all without the expense of RAC clusters.

N-way streams can also serve as a low-cost alternative to RAC, in low-DML systems. 

Some shops will place RAC nodes in separate buildings in the same neighborhood, but with the advent of the superfast dark fiber interconnect (Dense Wavelength Division Multiplexing (DWDM) technology), you can use Extended RAC and place RAC nodes up to 100 miles apart.  However, dark fiber is super-expensive, and most shops adopt a best practice where they combine RAC with disaster recovery solutions like n-way Streams replication.

With n-way Streams, geographically separate instances cross-feed each other using Streams replication.  Using this technique you can have high availability combined with disaster recovery and use automatic failover to redirect end-users if a single server in the Streams cluster fails.

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