Re: EMC and Tuning Oracle: Manuals are wrong?

You are right, EMC and your management
are wrong.

The manual is a little too black-and-white: with modern technology, properly applied, the need to worry about extreme separation has eroded somewhat - nevertheless the
redo logs, and archived redo logs on extremely hard-working systems still tend to suffer a different I/O pattern from the rest of the database.

The idea of letting 50% of each disc be used for something totally outside your control is very bad news - EMC seems to be good at pumping large chunks of data from place to place and very poor at small random I/Os, so the other activity could (transparently to you) guarantee that your application dies the death when 400 user are on.

BTW
> Database files
>are spread across four disk "sections" each of
>4Gb

Is this spreading done through striping at a fairly small stripe size - 4 chunks, one per disc would be bad news. Even so, with 400 concurrent users any large table spread over only 4 spindles is likely to be a performance I/O threat under any circumstances.

--

Jonathan Lewis
Yet another Oracle-related web site: www.jlcomp.demon.co.uk

benryan_at_my-deja.com wrote in message <7kc13c$23b$1_at_nnrp1.deja.com>...
>The Oracle Tuning Manuals (7 and 8) make some
>fairly clear statements about how Oracle files
>should be separated across disks.
>
>Example
>
>Oracle8 Server Tuning - 15-22 Section on
>"Separating Datafiles and Redo Log Files" says
>"Dedicating separate disks and mirroring redo log
>files are important safety precautions."
>
>EMC Technical Staff claim this does not apply to
>their systems.
>
>Any thoughts or comments would be appreciated?
>
>Ben Ryan - Oracle DBA
>
>P.S. We are running a "high-profile" production
>OLTP DB with currently over 100 users increasing
>to 400+ is the next few months. Database files
>are spread across four disk "sections" each of
>4Gb. Each physical disk is 8Gb, meaning the
>database (and operating system) only has half of
>each physical disk. Other half used by some other
>server, which I have no control over. My request
>for control over spindles to management has been
>rejected on the basis that there is no need for
>that level of control in an EMC environment. EMC
>Technical staff backed-up management's view.
>
>
>Sent via Deja.com http://www.deja.com/
>Share what you know. Learn what you don't.
Received on Fri Jun 18 1999 - 02:41:41 CDT