RE: Async and Direct I/O On Solaris using VXFS

  • From: "Jorgensen, Finn" <Finn.Jorgensen@xxxxxxxxxxxxxxxxx>
  • To: "'xrajx@xxxxxxxxxxx'" <xrajx@xxxxxxxxxxx>, "'kylelf@xxxxxxxxx'" <kylelf@xxxxxxxxx>
  • Date: Tue, 28 Jun 2011 08:33:47 -0400

I've done a fair amount of testing on Solaris and VxFS. I wouldn't call it 
exhaustive at all so you should do your own testing.

What I've found is that VxFS does not allow async IO regardless of what you do. 
Even ODM does not enable AIO. It enables directio without setting 
filesystemio_options and without setting convosync and mincache which has 
implications when accessing files in the filesystem outside Oracle (like a cp 
or mv). ODM, by the admission of a Sr Technical engineer from Veritas, is 
mostly good for certain types of scenarios. It wasn't worth the changes 
required and the amount of testing necessary in my environment.
The one thing that really made a difference for me was setting a kernel 
parameter called vmodsort(set vxfs:vx_vmodsort=1 in /etc/system). This 
parameter makes the fdsync kernel call a lot faster which really cut down on 
the CPU utilization on the servers and made IO a lot faster especially for apps 
using LOBs.


From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of rajesh koppada
Sent: Monday, June 27, 2011 6:29 PM
To: kylelf@xxxxxxxxx
Cc: Posting
Subject: RE: Async and Direct I/O On Solaris using VXFS

Thank you , sorry i missed the platform information , We are running on Sun 
Soalris 5.10 , Is there a similar way we can confirm that we are doing Async 
i/o ? or do we need to use special products like Oracle ODM or something to get 
Async i/o ?

Date: Mon, 27 Jun 2011 15:17:12 -0700
Subject: Re: Async and Direct I/O On Solaris using VXFS
From: kylelf@xxxxxxxxx
To: xrajx@xxxxxxxxxxx
CC: oracle-l@xxxxxxxxxxxxx

The tool "directiostat" looks pretty cool for sparc, on page

direct link at

On Mon, Jun 27, 2011 at 2:57 PM, kyle Hailey 
<kylelf@xxxxxxxxx<mailto:kylelf@xxxxxxxxx>> wrote:

What platform are you on? For direct I/O  on solaris check out


Another good reference<>

- Kyle<>

2011/6/27 rajesh koppada <xrajx@xxxxxxxxxxx<mailto:xrajx@xxxxxxxxxxx>>

How can i confirm that oracle will be doing Direct I/O and Asynchronous i/o 
with following options.
Database FILESYSTEMIO_OPTIONS is set to ALL which means to use,
setall - Enables both ASYNC and DIRECT IO
we are using VERITAS volume manager 5.0 with VXFS filesystems(We don't have QIO 
or ODM) and file system mount options are set as follows
mincache=direct and conovsync=direct
Will Oracle is going to use both direct i/o and asynchronous i/o with these 
file system options.
How can we ensure i am getting direct i/o and Async i/o ?
can we enable some trace or something just to ensure we are getting both?


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