Re: Why "Separating Data and Indexes improves performance" is a myth?
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 23 Apr 2004 18:13:44 +0100
And an old truism - which I think I first ran up the flagpole
during v6 days:
20 inserts might go into just one table block
20 inserts could easily mean 60 scattered index block
updates because you have 3 indexes on the table.
Ulimate Write ratio: 60 to 1
The last thing you want in some heavy duty write systems
is to separate index physical devices from table physical
devices. (note the hair-splitting description).
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
April 2004 Iceland http://www.index.is/oracleday.php
June 2004 UK - Optimising Oracle Seminar
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August 2004 Charlotte NC, Optimising Oracle Seminar
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----- Original Message -----
From: <Jared.Still@xxxxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Friday, April 23, 2004 5:46 PM
Subject: Re: Why "Separating Data and Indexes improves performance" is a
myth?
What matters is the performance of your system under load. If you have 10
disks in
a RAID 0 with all indexes and data residing on it and the performance is
somewhat
lackluster, splitting those disks into two 5 disk RAID 0 drives and
physically separating
the indexes and data will not improve performance.
It would be very likely though that it would decrease performance,
particularly on
full table scans and fast full index scans.
Jared
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