directio performance question

From: Max <trestusler_at_hotmail.com>
Date: 6 Jul 2003 04:56:53 -0700
Message-ID: <5a4548ca.0307060356.2c4c2c8a@posting.google.com>

Hi,

I've got what is probably for most of you a very basic question... From what I've read, in solaris, mounting an oracle filesystem with the
"forcedirectio" option gives it upto 80% of the performance of having oracle on raw devices by eliminating the double buffer.

I ran a small test and seem to get the opposite result. Can someone tell me if I am doing something wrong ?

without forcedirectio

---

SQL> set timing on
SQL> create index idx_dou_buff on INDEX_TEST(TIMESTAMP);

Index created.

Elapsed: 03:01:32.08

Then dropped the index, stopped orcle, unmounted the filesystems and remounted it with the directio option

With directio

---

SQL> create index idx_dou_buff on INDEX_TEST(TIMESTAMP);

Index created.

Elapsed: 03:58:27.01

WHy is an index creation taking more time with directio ?

Solaris 8 latest patches and Oracle 8i

Thanks for any comments.

M Received on Sun Jul 06 2003 - 06:56:53 CDT