RE: RAC in NAS

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
                
                --
                http://www.freelists.org/webpage/oracle-l

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