Re: Extended RAC and multicast

From: Tim Gorman <tim_at_evdbt.com>
Date: Wed, 16 Apr 2014 11:51:54 -0600
Message-ID: <534EC33A.9090005_at_evdbt.com>



Sorry to press, but do you know if they had evaluated Data Guard or Golden Gate at all? Did they really make such a decision based on a single piece of sales collateral?

I'm always shocked at how Oracle Corporation (and other vendors) will publish a white paper such as this, including a section on the "benefits of
<http://www.oracle.com/technetwork/products/clustering/overview/extendedracversion11-435972.pdf#page=6&zoom=auto,93,519>" without a balancing (and glaringly absent) "disadvantages of" section, which might include helpful cross-references to Oracle products Data Guard or Golden Gate. While there is brief passing mention of Data Guard in this paper, there is not a breath about Golden Gate. A "disadvantages of" section would have been the ideal way to steer customers for whom "extended RAC clusters" were not well-suited toward Data Guard or Golden Gate, both which are proven and widely implemented, which "extended clusters" are not.

The presence of only positive information about a product without any negative information ipso facto makes it a sales document, and worthless as a technical source.

On 4/16/2014 11:30 AM, Iggy Fernandez wrote:
> 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 Fernandez
> Email: iggy_fernandez_at_hotmail.com <mailto:iggy_fernandez_at_hotmail.com>
> Cellphone: (925) 478 3161
> Blog: So Many Manuals So Little Time
> <http://iggyfernandez.wordpress.com/>
> Author of Beginning Oracle Database 11/g/ Administration
> <http://books.google.com/books?id=pdSLnG66WQkC&printsec=frontcover#v=onepage&q&f=false>
> Editor of the /NoCOUG Journal <http://bit.ly/rC2gRA>/
> Lecturer at University of Washington Professional and Continuing
> Education <http://www.pce.uw.edu/biography/ignatius-fernandez/>
>
>
> ------------------------------------------------------------------------
> 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 <mailto:iggy_fernandez_at_hotmail.com>
> Cellphone: (925) 478 3161
> Blog: So Many Manuals So Little Time
> <http://iggyfernandez.wordpress.com/>
> Author of Beginning Oracle Database 11/g/ Administration
> <http://books.google.com/books?id=pdSLnG66WQkC&printsec=frontcover#v=onepage&q&f=false>
> Editor of the /NoCOUG Journal <http://bit.ly/rC2gRA>/
> Lecturer at University of Washington Professional and Continuing
> Education <http://www.pce.uw.edu/biography/ignatius-fernandez/>
>
>
> ------------------------------------------------------------------------
> From: martin.a.berger_at_gmail.com <mailto: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 <mailto:iggy_fernandez_at_hotmail.com>
> CC: oracle-l_at_freelists.org <mailto:oracle-l_at_freelists.org>;
> kulkarniravi_at_yahoo.com <mailto: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 <mailto: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
> <mailto:iggy_fernandez_at_hotmail.com>
> Cellphone: (925) 478 3161
> Blog: So Many Manuals So Little Time
> <http://iggyfernandez.wordpress.com/>
> Author of Beginning Oracle Database 11/g/ Administration
> <http://books.google.com/books?id=pdSLnG66WQkC&printsec=frontcover#v=onepage&q&f=false>
> Editor of the /NoCOUG Journal <http://bit.ly/rC2gRA>/
> Lecturer at University of Washington Professional and
> Continuing Education
> <http://www.pce.uw.edu/biography/ignatius-fernandez/>
>
>
> ------------------------------------------------------------------------
> Date: Mon, 14 Apr 2014 11:13:03 -0700
> From: kulkarniravi_at_yahoo.com <mailto:kulkarniravi_at_yahoo.com>
> Subject: Extended RAC and multicast
> To: iggy_fernandez_at_hotmail.com <mailto: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 - 19:51:54 CEST

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