Re: 2-node RAC faster than 6-node!

Hi,

well, I'd look for a reason why your application is CPU-bound. Excessive LIO + contention (with a most probable 'latch: cache buffers chains' and
'[gc]buffer busy', 'read by other session', etc) might be a root cause.

In such a case your application might be not scalable even in a single-instance configuration. And RAC is appropriate only for scaling "scalable applications". Sorry for the tautology.

Everything previously said is a GUESS (sorry, Alex). Please, provide ANY info about instance's performance statistics. The head (200-300 lines) of the results of @?/rdbms/admin/awrrpt would nice.

--Andrey

A Ebadi wrote:
> We have an existing 4-node RAC cluster (v440's on Solaris & Oracle
> 10.2 w/ ASM) that was big time CPU-bound and application performance
> was suffering. We added 2 new nodes(M5000's) to bring the total to 6
> and the app performance actually went down significantly! After
> messing around with it we found out that by taking the original 4
> nodes out of the picture & only running on the 2 new M5000's nodes
> things improved significantly - the app jobs started running in some
> cases 20X faster than ever! We tested adding just a single node
> (v440) back in the mix and performance went way down immediately, so
> we decided to keep things running on just the 2 M5000's for now.
>
> Any suggestions on identifying root cause as to why the adding of any
> nodes back to the picture slows things way down? We have an SR
> opened with Oracle Support but nothing firm so far.
>
> Thanks,
> Abdul
>
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