Re: RAC cache fusion details

From: DA Morgan <damorgan_at_psoug.org>
Date: Wed, 19 Dec 2007 08:55:59 -0800
Message-ID: <1198083353.985699@bubbleator.drizzle.com>

Jerome Vitalis wrote:
> DA Morgan wrote:
>

>> Jerome Vitalis wrote:
>>> DA Morgan wrote:
>>>
>>>> Yes.
>>> Did you publish the results anywhere on the web?
>>>
>>> TIA

>

>> Have you read Oracle's license? <g>

>
> ;-)
>
> From what we can read on the web about block sharing (e.g.
> http://www.pythian.com/blogs/282/oracle-rac-cache-fusion-efficiency-a-buffer-cache-analysis-for-rac
> ), it's difficult to imagine any real-life database whose performance
> would not suffer (maybe to a limited extent in the best cases) from being
> turned into a RAC database.
> The possible advantages provided by the huge global cache are probably not
> so important in regard of the waits introduced by block sharing. Of course
> RAC can provide other advantages such as distributed parallel execution.
> But if a single server already has enough hardware resources (CPU, RAM, IO
> bandwidth...) to handle the workload, it's difficult to see how a
> migration to RAC could not hinder the performances (again: with
> "unpartioned" apps).
>
> That's why I wanted to know if we could find the results of such test
> cases anywhere on the web.

Oracle does not sell Oracle as a high performance enhancement. They sell it for high availability. Oracle's own published numbers for E-Business Suite 11i show scalability at 84%.

What one big-iron box gives you is very high initial expense, very high upgrade costs, very high maintenance costs, and the realization that, at minimum, you need to purchase two or three of them of which all but one will be idle 99.99% of the time to achieve HA.

What RAC gives you is good scalability using inexpensive commodity hardware. Incremental and affordable scalability. Highly flexible configuration. And most importantly load balancing and transparent failover.

If you are going to buy the technology buy it for its intended purpose.

-- 
Daniel A. Morgan
Oracle Ace Director & Instructor
University of Washington
damorgan_at_x.washington.edu (replace x with u to respond)
Puget Sound Oracle Users Group
www.psoug.org

Received on Wed Dec 19 2007 - 10:55:59 CST