Re: EMC and Tuning Oracle: Manuals are wrong?

I simplified the actual situation a little bit. There are infact 8 physical disk setup as mirrored pairs. (i.e. 4 logical disks) The Oracle Database has half of each logical disk. The tablespaces are spread across the disks in the traditional way, (tables are separated from indexes, redo logs on their own. system, rbs, temp squashed on to the remaining disk). The other servers are Novell and Windows-NT servers performing as file and print servers. Which bothers me even more because there will no particular pattern to the disk I/O on these servers! Oh, the EMC only has 1Gb of cache, the minimum!

In article <929691936.29147.1.nnrp-13.9e984b29_at_news.demon.co.uk>,   "Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote:
> 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.
>
>

Sent via Deja.com http://www.deja.com/
Share what you know. Learn what you don't. Received on Fri Jun 18 1999 - 14:40:47 CDT