New forcedirection Mount Option in Solaris

I was scanning a manual for a software product that runs on top of Oracle the other day and I ran across some “best practices” for Oracle. I was surprised to see a new mount option that I hadn’t run across before. Apparently it makes sequential reads 10-15% faster. See below for the section of the SERVER PREPARATION GUIDE for IBM Prospect® for Alcatel-Lucent Release 33.

Using forcedirection to Increase Performance

Sun Microsystems best practices for Solaris and Oracle installations recommends using the forcedirection mount option for file systems that store Oracle data files. The forcedirection option forces input/output (I/O) operations to bypass Solaris file buffering and caching. The bypass lets you combine the performance benefits of raw file systems with the manageability and flexibility of traditional file systems. The forcedirection option typically results in 10 percent to 15 percent faster sequential reads.

Caution! Use the forcedirection option on Solaris UNIX file systems. Other third-party file
systems provide similar functionality. If you are using a third-party file system, such as Veritas,
consult the company documentation for instructions on turning off file system buffering.

To set up the forcedirection option on existing IBM Prospect servers

1.Edit the


file to include the forcedirection option using the root account.
$ su root
2.The seventh column in /etc/vfstab is the mount option column. In this column, change the value from – to forcedirection for the file systems containing Oracle data files. For standard installations, these are file systems /u02 through /u06. For example:
/dev/dsk/c2t0d0s6 /dev/rdsk/c2t0d0s6 /u02 ufs 3 yes –
IBM Prospect® for Alcatel-Lucent Release 33
Installing and Configuring Solaris
© Copyright IBM Corp 1999, 2009. All rights reserved.
SPG – Page 28
/dev/dsk/c2t0d0s6 /dev/rdsk/c2t0d0s6 /u02 ufs 3 yes forcedirection
Caution! For standard installations, enable forcedirection on file systems /u02 through
/u06 only. Do not enable forcedirection on file system /u01 — the /u01 file system
does not contain Oracle data files.
3.The forcedirection setup changes occur during the next system reboot. These changes are only a performance improvement; if they are the only changes requiring a reboot, schedule the reboot for the next available maintenance period. For information about scheduled maintenance, see the Administration Guide.
4.For a setup using forcedirection, use mount table entries in /etc/vfstab as follows:
/dev/dsk/c0t0d0s7 /dev/rdsk/c0t0d0s7 /u01 ufs 2 yes –
/dev/dsk/c2t0d0s6 /dev/rdsk/c2t0d0s6 /u02 ufs 3 yes forcedirection
/dev/dsk/c2t1d0s6 /dev/rdsk/c2t1d0s6 /u03 ufs 3 yes forcedirection
/dev/dsk/c2t2d0s6 /dev/rdsk/c2t2d0s6 /u04 ufs 3 yes forcedirection
/dev/dsk/c2t3d0s6 /dev/rdsk/c2t3d0s6 /u05 ufs 3 yes forcedirection
/dev/dsk/c2t4d0s6 /dev/rdsk/c2t4d0s6 /u06 ufs 3 yes forcedirection

If you’ve made it this far I have to go ahead and let you know that there is no forcedirection mount option (as far as I know). I think the editor of the manual (or maybe an overactive spell checker) got a little carried away – it should have been forcedirectio. Happy April Fools Day!


  1. Kevin says:

    This is one particular spell check snafu bogs me down quite frequently… the moment I started reading this I thought, hmmm, spell-checker headaches :-)

  2. osborne says:

    Hey Kevin,

    Thanks for dropping by. Yeah, originally I didn’t have the note at the bottom, but then I got a little nervous when I Googled for forcedirection and got a bunch of links to my post looking like it was a real thing. Thought I’d better add the note. Takes some of the fun away, but at least no one will be misled if they don’t bother to look at the comments.


  3. joel garry says:

    LOL! Telling your filesystem “You WILL go south!”

    Googling for SERVER PREPARATION GUIDE for IBM Prospect® for Alcatel-Lucent Release 33 comes up with a real doc entitled Title Goes Here Second Line Goes Here

    words: absconds page

  4. Andy says:

    This is a surprise. I hope it really is an Aprils’ Fools joke, because this was a product I supported … ;)

  5. Andy says:

    Looks like the same error persists in R34 doc as well :p Thanks for spotting that!

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