Re: RAC node distance

  • From: Steve Baldwin <stbaldwin@xxxxxxxxxxxxxxxx>
  • To: veeeraman@xxxxxxxxx
  • Date: Thu, 25 Mar 2010 15:08:46 +1100

Hi Ram,

I have no experience with 'geo-clusters' but we do use RAC so for what
it's worth ...

In my opinion this is a bad idea.  No advantages, only disadvantages.
Keep in mind that each cluster node needs at least 3 separate network
connections - one for the interconnect, one for shared storage
(assuming you are using iSCSI - don't even know *if* you could do it
with fiber channel) and one for the client network.  Having 3 (min -
ideally more for redundancy) separate high speed (min 1 Gb, ideally
higher) networks spanning 3 city blocks sounds expensive and doesn't
buy you anything anyway.  Where are you putting the shared storage -
in a third building?  If they think this offers some kind of DR
solution they are sadly mistaken.  A DR solution needs to duplicate
*everything*.  Servers, shared storage, network infrastructure, ...
Putting a single RAC node 3 blocks away is not something I would
consider (unless you can give us more insight into their reasoning).



On Thu, Mar 25, 2010 at 2:20 PM, Ram Raman <veeeraman@xxxxxxxxx> wrote:
> Hi
> We have a 2 node RAC for one of our new applications. There are 2 sets
> of application/web servers; each set located on different building separated
> by about 3 city blocks. But, both the RAC nodes are in one of the buildings.
> The management seemed to be inclined to want to separate them in different
> buildings. To me that does not sound like a great idea, with interconnect
> traffic and such. Questions:
> 1) Are there any sites that use RAC 'geo-cluster' mode?
> 2) Would running the RAC in 'active-passive' mode help in case of geo
> cluster type solution? What kind of interconnect is used by sites that have
> geo cluster type RACs?
> PS. I am aware that RAC is not a DR solution, going for a dataguard would be
> a good DR solution.
> Ram.

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