Re: directio performance question

On our dev environment, I noticed significant improvement (around 25%) in disk based sorts (specifically improvements in "direct path write" event) after mounting the filesystem in "forcedirectio" mode. Apart from bypassing the file system buffers, this option also eliminates the single writer lock (at the unix level) resulting in better performance.

-Madhu S

trestusler_at_hotmail.com (Max) wrote in message news:<5a4548ca.0307060356.2c4c2c8a_at_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 Tue Jul 08 2003 - 14:06:57 CDT