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Re: Direct io (mincache and convosync) not working?

 
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Re: Direct io (mincache and convosync) not working?

OK, now I'm doubting what I told you!

Just read an Oracle metalink article (555601.1 if you or your DBA has access).

Now I don't have 100% faith in the accuracy of metalink articles, but this one does suggest you should see O_DIRECT in the open call...

So a couple of questions...

1. This is a tusc trace of a database writer process isn't it? (ora_dbw*_*)

2. What is the oracle parameter "filesystemio_options" set to??

Sorry I can't test this myself until next week...

HTH

Duncan

I am an HPE Employee
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Danny Petterson - DK
Trusted Contributor

Re: Direct io (mincache and convosync) not working?

Thanks again for your prompt replies.

1) Yes, precisely

2) filesystemio_options has been tried with "setall" and "directio" - no difference.

Greetings
Danny

Re: Direct io (mincache and convosync) not working?

What does:

pfiles

say?

e.g. if your dbw PID is stil 17520

pfiles 17520


HTH

Duncan

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chris huys_4
Honored Contributor

Re: Direct io (mincache and convosync) not working?

Hi,

Im also not so sure, what tusc should show, but I do know that the tusc output isnt directly corresponding with the mount output in the "opening statement".

I.e. in the mount output, "/oracle/ORADB1/databases" output is shown and in the tusc output, "/oracle/ORADB2/databases" output is shown, what unless the 2 directories are linked somehow, looks like different mountpoints.

Also normally for oracle databases, you only want direct IO for oracle database access and buffered IO for all "other access". And for direct IO, for only oracle database access, convosync=direct is enough.

NOTE: what definitely will show if direct IO is used, is kitrace output, but for being able to interprete the kitrace output you will need a call logged with HP support.

Greetz,
Chris
Volker Borowski
Honored Contributor

Re: Direct io (mincache and convosync) not working?

Hi,

is this open-flag still relevant with async in place?
If async is used, db_wr talks to the async driver,
which should do the effective IO
depending on the mount options.

I think you might just see the expected options in open, when you disable async and configure the old fashioned io_slaves???
(guessing)

Volker

Re: Direct io (mincache and convosync) not working?

Volker,

I don't think async can be in place... unless I'm mistaken async either happens on raw/ASM or when using ODM which requires VxVM.

this appears to be on a filesystem on an LVM logical volume, so I can't see that async could be used...

HTH

Duncan

I am an HPE Employee
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Danny Petterson - DK
Trusted Contributor

Re: Direct io (mincache and convosync) not working?

Hi guys!

I really appreciate all the comments.

Duncan - pfiles for the databasewrite shows this for all database-files using this mountpoint;
flags = O_RDWR|O_DSYNC|O_LARGEFILE|O_EXCL

...and yes, its a vxfs-filessytem on a lvol.

Chris - We only use convosync=direct on mountpoints with database-files

Hope we are getting there :-)

Greetings
Danny
Volker Borowski
Honored Contributor

Re: Direct io (mincache and convosync) not working?

Hi Duncan,

is that still true? I thought that restriction
is outdated meanwhile. But I did not check
recently directly at Oracle.

Volker

2004: http://www.oracle.com/technology/deploy/performance/pdf/TWP_Oracle_HP_files.pdf

See 5.1.1.

On HP-UX, asynchronous IO is only supported with a raw device (raw disk partition or raw logical volume), although this will change with HP-UX 11i v3 (internally known as 11.31).

2006: http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=992511&admit=109447626+1274960107832+28353475

Re: Direct io (mincache and convosync) not working?

Volker,

Yes and No!

I think that WP is possibly old enough to have expected 11iv3 to have AdvFS with I think supported async IO - of course we never did get AdvFS on HP-UX.

We do now have concurrent IO, with VxFS5.01 on 11iv3 which delivers near raw performance. I've not had the opportunity to understand CIO properly and understand if it is just another name for AIO, but it does sound similar to my (simple) mind. There's a WP on it here:

http://www.hp.com/go/ojfsperf

Of course in this case Danny isn't using cio, as it would have shown up as one of his mount options...

HTH

Duncan

I am an HPE Employee
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Re: Direct io (mincache and convosync) not working?

Danny,

Sorry but I really can't do anything else now until I can get back to my test system in the UK - that will be next week.

Did you get a call logged with the RC?

HTH

Duncan

I am an HPE Employee
Accept or Kudo