RE: RAC in NAS

>> 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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