How to change VxFS filessystem mount options Online?

[Gulam Mohiuddin]

How to change the following VxFs filesystem mount options Online:

nodatainlog, mincache=direct,convosync=direct

After changes were made how to check and confirm the new mount options.

Then later how to revert back above option online again to original state.

We have Online JFS 3.3 on HP-UX 11i.

The filesystem is only used for Oacle9i datafiles.

I am testing Oracle datafile performance.


Thanks,

Gulam.

[Jeff Schussele]

Hi Gulam,

You need JFS 3.3 ver4 to do this.
Check the version with:
fstyp -v /dev/vg_name/lv_name | grep version
Then IF it's version 4 then the command is:
mount -F vxfs -o remount,nodatainlog, mincache=direct,convosync=direct /mnt_point
The remount option is the key.

HTH,
Jeff

[Steven E. Protter]

I don't think I'd change the mount options on a filesystem with an active oracle database running on it, even if OnlineJFS could do that.

I'd shut the database to avoid possible data corruption. Maybe I'm just cautious. Once the database is shut down, you can change the mount options the old fashioned way, by using umount and mount.

SEP

[Jeff Schussele]

It's perfectly safe - I've done it many times w/o any problems whatsoever.
Any disk I/O in the queue at the time of the command will use the "old" options & any requests queued after use the "new" options.
BUT you have to have JFS 3.3 version 4 - or higher - to use -o remount.
IF the version is less than 4 then vxupgrade must be used and *this* is the one where caution should be used & the DB sould probably be down. Also it must be noted that you can't go from ver2 straight to ver4. Must go to ver3 & *then* go to ver4.

My $0.02,
Jeff

[A. Clay Stephenson]

You can't. You will have to umount the filesystem and then mount it again with the -o options specified. Of course, before doing this, you must first shutdown the database.

Assuming that you have a generous amount of memory in this box, you are not going to see much benefit (if any) from these mount options under 11.11. Previous versions (especially 10.20 and 11.0 to a lesser extent) benefitted from bypassing the buffer cache but my tests have shown under 11.11, Oracle performs best with fully cooked files.

[Jeff Schussele]

I hate to contradict you Clay but this dog *can* hunt with the proper JFS layout version.

And a final note to Gulam - Make *sure* the DBAs have a properly sized SGA to handle the DB buffering because that's going to be the *only* buffer that I/O will get at that point.

Rgds,
Jeff

[A. Clay Stephenson]

Ooops, since you are running OnlineJFS 3.3, you can use the remount option but again, I think you are going to find that this is a waste of time under 11.11.

[Gulam Mohiuddin]

Thanks everybody.

One last thing,how to revert it back online?

Thanks,

gulam.

[Jeff Schussele]

OK - before you change it do a
mount -v
and not the options as they are now.
Then when going back just do
mount -F vxfs -o remount,???log,mincache=???,convosync=??? /mnt_point
replacing the ??? with the current settings.
Simple as that.

HTH,
Jeff