Re: RAC in NAS

  • From: "Mark Brinsmead" <pythianbrinsmead@xxxxxxxxx>
  • To: dbvision@xxxxxxxxxxxx
  • Date: Fri, 28 Jul 2006 21:55:40 -0400


  You are only *half* right, I fear.

  Actually, at least one of -- and perhaps both -- MetaLink and Werner
describe more or less
the same caveat, that is:  applications *other* than Oracle may be
responsible for the non-zero
counts in slabinfo.

  But here's the half where you're wrong.  (Or at least, not completely
"right".)   Those hypothetical
"other" applications can just as easily be resposibly for the *increases* in
the slabinfo stats as
they are they would be for "non-zero" values.  After all, those values had
to increase from zero
*some* *time*, didn't they.  ;-)

  Anyway, you are correct about this:  I am still unaware of a simple way
to prove *conclusively*
that a database is actually using Asynch I/O.  But (on a good day) I now at
least know how to
prove that it is *not*.  (Or at least that *no* databases *are*.  Sadly,
multiple database on the
same host muddy the water even more.)

  If anybody out there can tell me of a simple (and reliable) test that
*proves* a database is using
Asynch I/O, I'd like to hear about it...

  In the meantime, it has (happily) met my purposes to be able to prove the

On 7/28/06, Nuno Souto <dbvision@xxxxxxxxxxxx> wrote:

Mark Brinsmead wrote,on my timestamp of 28/07/2006 1:39 PM:

> (Almost) just for chuckles, I opened an SR with Oracle support, asking
> questions like "how can
> I test whether my DB is doing Asynch I/O on Linux?" and "knowing that
> Asynch I/O is unsupported,
> what are the risks of doing so anyway?".  After almost two weeks, the
> questions are unanswered,
> even though I was able to answer them myself with less than an hour of
> surfing Metalink and Google.

yes, there is a note in metaclick explaining how to check.
But it's not complete, neither is werner's site:
you check for those counters in /proc/slabinfo being
non-zero *AND* changing in value when you startup Oracle!
There might be *other* software around already using aio
and just having them as non-zero is not enough to say
Oracle is using it.


-- Cheers Nuno Souto in (finally) sunny Sydney, Australia dbvision@xxxxxxxxxxxx --

-- Mark Brinsmead
  Staff DBA,
  The Pythian Group

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