RE: Extended RAC and multicast

From: Iggy Fernandez <iggy_fernandez_at_hotmail.com>
Date: Wed, 16 Apr 2014 10:30:13 -0700
Message-ID: <BLU179-W429CF85DCF602B2EB9F39EB530_at_phx.gbl>



Hi, Tim,
The customer bought the story (in the Extended RAC white paper) that Extended RAC provides some measure of Disaster Recovery (with the emphasis on some). The white paper is at http://www.oracle.com/technetwork/products/clustering/overview/extendedracversion11-435972.pdf.
"Unlike classic Oracle RAC implementations, which are primarily designed as scalability and high availability solution that resides in a single data center, it is possible under certain circumstances to build and deploy an Oracle RAC system in which the nodes are separated by greater distances. For example, if a customer has a corporate campus, they might want to place the individual Oracle RAC nodes in separate buildings. This configuration provides a higher degree of disaster tolerance, in addition to the normal Oracle RAC high availability, since a fire in one building would not, if properly set up, stop the database from processing. Similar, many customers have two data centers in reasonable proximity (<100km) which are already connected by a direct, ideally non-routed, high speed link(s) and are often on different power grids, flood plains, and the like."
"Oracle RAC on Extended Distance Clusters does not constitute a different type of cluster, neither is there a special installation option that one can choose from. This means that as far as the configuration of the system is concerned, the main goal is to hide the fact that Oracle RAC is now operating over distance. On the other hand, this means that the basic configuration remains the same, including its requirements. Attention must be paid when configuring the network and storage connectivity for Extended Distance Oracle RAC environments."
Iggy
  • Iggy FernandezEmail: iggy_fernandez_at_hotmail.comCellphone: (925) 478 3161Blog: So Many Manuals So Little Time Author of Beginning Oracle Database 11g AdministrationEditor of the NoCOUG JournalLecturer at University of Washington Professional and Continuing Education

Date: Wed, 16 Apr 2014 09:36:25 -0600
From: tim_at_evdbt.com
To: oracle-l_at_freelists.org
Subject: Re: Extended RAC and multicast


  
    
  
  
    Iggy,

      

      Not to open any cans of worms (and please feel free to not answer
      this question for any reason), but why did they choose an
      "extended RAC" deployment in the first place, as opposed to any of
      the Data Guard options?  Do they already use Data Guard?  Was
      there something that "extended RAC" (or "geographically-dispersed
      cluster" technology) does better than Data Guard (or database
      replication technology) in general?

      

      Just curious...

      

      Thanks!

      

      -Tim

      

      

      
      On 4/16/2014 9:21 AM, Iggy Fernandez wrote:

    
    
      
      Thank you
          very much Martin.
        

          
        We found additional
            information on the multicast requirement at the following
            link:
        
          

            
          http://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/UCS_CVDs/cisco_ucs_oracle_rac.html#wp439295
          

          
          Kindest regards,
          

          
          Iggy
          

            -- 
            Iggy Fernandez
            Email: iggy_fernandez_at_hotmail.com
            Cellphone: (925) 478 3161
            Blog: So Many Manuals So Little Time
              
            Author of Beginning Oracle Database 11g
                  Administration
            Editor of the NoCOUG Journal
            Lecturer at University of Washington Professional
                  and Continuing Education
            

            

            
              From: martin.a.berger_at_gmail.com

              Date: Mon, 14 Apr 2014 20:46:39 +0200

              Subject: Re: FW: Extended RAC and multicast

              To: iggy_fernandez_at_hotmail.com

              CC: oracle-l_at_freelists.org; kulkarniravi_at_yahoo.com

              

              Iggy, Ravi, 
                 
                from all my test I call multicast a requirement
                  from 11.2.0.2 onwards. 
                Take care about the different Multicast networks
                  possible in different Patch-Sets! 
                As you are talking about VLAN_S_ - I'd not do
                  anything than pure switched private network.
                  Everything else will lead to troubles sooner or
                  later. 
                

                
                My .02
                 Martin 
                   
                

                  

                  On Mon, Apr 14, 2014 at
                    8:29 PM, Iggy Fernandez <iggy_fernandez_at_hotmail.com>
                    wrote:

                    
                      
                        
                          A friend
                              asked me a question that I could not
                              answer. He is in the planning stages of an
                              "extended RAC deployment" and is looking
                              for confirmation that multicasting is
                              optional.
                          

                            
                          Help would
                              be appreciated.
                          

                            
                          Kindest
                              regards,
                          

                            
                          Iggy
                          

                          -- 
                          Iggy Fernandez
                          Email: iggy_fernandez_at_hotmail.com
                          Cellphone: (925) 478 3161
                          Blog: So Many Manuals So
                                Little Time
                            
                          Author of Beginning Oracle
                                Database 11g Administration
                          Editor of the NoCOUG Journal
                          Lecturer at University of Washington
                                Professional and Continuing Education
                          

                          

                          
                            Date: Mon, 14 Apr 2014 11:13:03 -0700

                            From: kulkarniravi_at_yahoo.com

                            Subject: Extended RAC and multicast

                            To: iggy_fernandez_at_hotmail.com

                            

                            I am looking to setup
                              extended RAC for my client. The details
                              are as following:

                              

                              The two data centers are separated by a
                              distance of less than 20 miles.

                              

                              They are connected by a high speed
                              dedicated connection. 

                              

                              Operating System: RHEL 6 64 bit

                              

                              Database version: 11gR2 (11.2.0.3)

                              

                              Hardware: Four servers with 4x16
                              configuration

                              

                              All the documentation I have reviewed so
                              far says multicast should be enabled on
                              the private interconnect between all the
                              nodes

                              of a RAC database. However, my network
                              resources tell me that multicasting is not
                              enabled across the data centers and VLANs

                              do not span across the data centers. The
                              only reference I have seen to multicasting
                              requirement is in this Oracle document:

                              

                              http://docs.oracle.com/cd/E16655_01/install.121/e17888/networks.htm#CWLIN476
                                
                              Specifically it makes the following
                              assertion:

                              

                              "You do not need to enable multicast
                              communications across routers"

                              

                              Does this mean, multicast is optional?

                              

                              Regards,

                              

                              Ravi Kulkarni

                              

                            
                          
                        
                      
                    
                  
                  

                
              
            
          
        
      
    
    
 		 	   		  
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Received on Wed Apr 16 2014 - 19:30:13 CEST

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