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Re: New challenge - clustering - do I understand this correctly?

From: Ed Stevens <nospam_at_noway.nohow>
Date: Tue, 12 Aug 2003 08:00:52 -0500
Message-ID: <n2ohjv0klcmoee9i6jg9f6fga5ir68hfe3@4ax.com>


On 11 Aug 2003 20:36:24 -0700, wizofoz2k_at_yahoo.com.au (Nuno Souto) wrote:

>Ed Stevens <nospam_at_noway.nohow> wrote in message news:<jo4gjvsv17mr0j8jqo2p7a04pbb5c6s7bg_at_4ax.com>...
>
>> With OPS, you have two concurrently instances against the same
>> database. They can both be accessed concurrently for load balancing
>> or whatever. If one fails, SQLNet (if correctly configured) will
>> reconnect everything to the surviving instance.
>
>which will then rollback any interrupted transactions in the
>failed instance, as well as releasing locks, etcetc.
>
>
>>
>> Do I have this right?
>
>In a nut shell, yes.
>
>> If so, are there pros and cons that might not be immediately obvious.
>
>HA won't scale without replacing hardware by faster/more capacity one.
>
>OPS/RAC won't scale linearly for heavy concurrent update activity,
>but this can be compensated for by design. Otherwise, just add
>more of the same boxes at any time.
>
>
>> What I see is that the HA option can result in a few minutes of outage
>> during the switch, but is much easier for the DBA to adminster -- it
>> would be handled just like any other single machine DB and all cluster
>> activity and recovery from node failure is handled by the OS --
>> transparent to Oracle. On the other hand the OPS option is more
>> complicated for the DBA to administer, but can result in near zero
>> down time.
>
>I don't understand how you can think RAC/OPS is harder on the
>administrator. All that happens is that a second instance
>recovers transactions from the failed instance. All else runs
>along same old same old. What in that requires "complication"
>from the administrator?
>

I can think that RAC/OPS is harder on the administrator because I've never done one. You never know what it is you don't know, and I'm staring into the abyss at this point. In short . . . fear of the unknown.

>Now if you're talking *setup*, yes, there is a possibility
>things will be slightly more complex to get started with RAC.
>But that is a once-only effort: hire a good reputation consultancy
>to help you with it and be done. That's where consultants add value:
>once-only requirements.
>

Ah, but what if one *is* the consultant? (So to speak).
>
>As for efficiency, picture this:
>
>- you get a new car.
>- your wife gets a new car.
>- you follow your wife everywhere a coupla minutes behind her,
>so that you can pick her up if something goes wrong with her car.
>- she does the same to you.
>
>or
>
>- you buy a new car.
>- your wife buys a new car.
>- you go to work, she goes shopping.
>- any probs, one of you calls the other
>and picks him/her up.
>

I see your point, and after conifirming that I had a basic grasp of the two architectures (I know, I know . .. buzzword de juor) i agree. Unfortunately, that's not my decision. I can offer opinions, but ultimately I have to implement whatever the "project architect" (yes, that's really his title) decides on. What drives that decision, I'm not sure. Could be requirements of the application middleware which will also reside on these servers. Or it could be lunch with a market rep, or the influence of the latest magazine article. (The latest trend -- uh, paradigm -- in management: Management by Magazine Article (tm)"

>
>Which option would you rather?
><okok, no "Antonio Banderas" replies!> :D
>
>
>Cheers
>Nuno Souto
>wizofoz2k_at_yahoo.com.au.nospam
Received on Tue Aug 12 2003 - 08:00:52 CDT

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