RE: RAC in NAS
- From: "Kevin Closson" <kevinc@xxxxxxxxxxxxx>
- To: "Frits Hoogland" <frits.hoogland@xxxxxxxxx>
- Date: Sat, 29 Jul 2006 11:49:15 -0700
it simulates skgfaio in threads...no matter, still a good lower-half
test
________________________________
From: Frits Hoogland [mailto:frits.hoogland@xxxxxxxxx]
Sent: Saturday, July 29, 2006 9:40 AM
To: kevinc@xxxxxxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: RAC in NAS
exactly my point!
I've seen oracle doing async IO with the 2.4 kernel doing other
system calls (the kludgy stuff you mentioned), and oracle doing async IO
with the 2.6 kernel (io_submit system call).
Ever looked at orion in conjunction with linux? It doesn't seem
to do async IO.
frits
On 7/29/06, Kevin Closson <kevinc@xxxxxxxxxxxxx> wrote:
>> on the other hand, if the system call is
the same, what
kind of magic is involved which makes oracle do
asynchronous IO? The
system call must tell the operating system what kind of
IO it wants to
do, either by doing a call which implies the kind of
synchronousity, or
by setting a flag which alters the synchronousity.
...but the calls are not the same. If you strace 10g
DBWR, after linking
in
libaio and setting filesystemio_options=direcIO, you
will see
io_submit(2)
calls which are new to 2.6 kernel. There really was no
"real" async IO
prior to the 2.6 kerenl. There was some kludgy stuff
piggy-packed on
the socket interface of all things, but it was crazy.
Then , of course, if $ORACLE_HOME/lib/libodm* is a real
ODM library you
get
async IO regardless of what libaio is and regardless of
what init.ora
parameters you set...when ODM is linked in, all the
"async*" init.ora
params
are no-ops and filesystemio_options doesn't do anything
either. You just
get
async IO
--
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