Re: Using Direct I/O Filesystem for Oracle Database
- From: David Miller <David.J.Miller@xxxxxxx>
- To: Junior DBA <juniordba2004@xxxxxxxxx>
- Date: Tue, 15 Jan 2008 13:25:00 -0600
Hi Muhammad Salman Faheem,
You should be getting directio with the setup you have using just
"setall". You can verify this by doing "truss -f" on the startup
call and looking at the calls mentioned on the website, i.e. the
open, directio and ioctl. That's really the only way to do it.
There currently is no Solaris utility to display the status of
a file (that I know of).
If you do truss, you'll want to carefully match the file descriptor
number returned by open() with the file descriptor passed to directio()
or ioctl() to be sure the calls are happening on the appropriate files.
There were some versions of Oracle and versions of Solaris where
"setall" was not sufficient, but they were older versions. With
10g R1 and Solaris 9 9/05, that shouldn't be the case, so you should
be fine.
But as other posters have mentioned, just using directio may or may
not affect your overall performance. You'll need to monitor the
application to see how it responds.
And as I mentioned, if you do use directio, you may need to increase
the data buffers in the SGA since you will not be buffering data in
the filesystem cache any more and so may need to cache them in the
SGA.
Regards,
Dave Miller
Junior DBA wrote, On 01/14/08 23:54:
BismillahirRehmanirRahim
Hi David Miller,
The output i pasted in my last email was taken from someone posted ,
and i gave the link to that post. so i just wanted to know the
authencity of the claimed the poster made that "Oracle still dont
use direct I/O with filesystemoption_io=setall."
Our Filesystem is ufs, we are running Oracle 10g R1 on Sun Sparc V890
Solaris 2.9.
After doing little research on Direct I/O i found out that
filesystemoption_io=setall is only required thing to enable oracle to
use Direct I/O for datafile Access. [ you also suggested that ]
And there is no need to mount Datafiles ufs filesystem with
forcedirectio option.
Infact our Vendor Recommended to mount Oracle Datafiles ufs Filesystems
with
forcedirectio, whereas i decided to handle direct I/O at Oracle Level.
In my understanding its more efficient and appropriate to use
filesystemoption_io=setall than to mount whole filesystem with
forcedirectio, as it will do direct I/O on per datafile basis instead of
per filesystem basis [ as in case of forcedirectio mount option.]
Moreover with filesystemio_options=setall , the backups and other
command [ e.g. cp , mv , compress ] would still use buffered I/O and
wont get slower.
I need experts comments on using filesystemio_options instead of
forcedirectio mount option.
also i need to know how can ensure that Oracle is using Direct I/O with
filesystemio_options=setall ,
and how can i compare the I/O performance with
filesystemio_options=setall and with forcedirectio mount option ? which
is recommended .
the output of /etc/release is pasted below.
Thanks for your support & time.
Your DBA Colleague
Muhammad Salman Faheem
[oracle@sun:ORCL oracle]$ more /etc/release
Solaris 9 9/05 s9s_u8wos_05 SPARC
Copyright 2005 Sun Microsystems, Inc. All Rights Reserved.
Use is subject to license terms.
Assembled 04 August 2005
--
//www.freelists.org/webpage/oracle-l
Other related posts:
