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Good test - which exhibits an interesting point: when you quadrupled the number of discs, you only doubled the performance.
Of course, the conclusions you may draw
from the test depend on the activity - but
it does suggest that there is mileage in
thinking carefully about how to make best
use of the available spindles.
Possible explanations that could fit your observation:
Your test was read only, so the spindles for undo and redo were effectively inactive so the effective spindle count was only doubled.
Your test was I/O bound on one disc, but required only a little extra I/O capacity to become CPU bound
Your test was write-intensive, but you had lots of indexes on the updated tables, so the index-holding disc became the I/O bottleneck before you go close to capacity on the other three.
Your test was highly concurrent with lots of very small updates on tables that did not affect indexes - so your bottleneck was in the redo log allocation and redo log buffer.
-- Regards Jonathan Lewis http://www.jlcomp.demon.co.uk The educated person is not the person who can answer the questions, but the person who can question the answers -- T. Schick Jr One-day tutorials: http://www.jlcomp.demon.co.uk/tutorial.html ____Iceland__November (tbc) ____Belgium__November (EOUG event) ____UK_______December (UKOUG conference) Three-day seminar: see http://www.jlcomp.demon.co.uk/seminar.html ____USA__October ____UK___November The Co-operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html "Geomancer" <pharfromhome_at_hotmail.com> wrote in message news:cf90fb89.0310100430.7c362905_at_posting.google.com...Received on Sat Oct 11 2003 - 09:03:37 CDT
> In my experience with Oracle on Windows, I demonstrated significant
> slowdown with the whole database on a single non-RAID disk.
>
> When I moved indexes to a separate disk, undo to another and redo to
a
> 4th disk, performance doubled!
>