On Wed, Mar 07, 2001 at 12:03:41PM -0800, Mikheev, Vadim wrote:
> Ian wrote:
> > > I feel that the fact that
> > >
> > > WAL can't help in the event of disk errors
> > >
> > > is often overlooked.
> >
> > This is true in general. But, nevertheless, WAL can be written to
> > protect against predictable disk errors, when possible. Failing to
> > write a couple of disk blocks when the system crashes
or, more likely, when power drops; a system crash shouldn't keep the
disk from draining its buffers ...
> > is a reasonably predictable disk error. WAL should ideally be
> > written to work correctly in that situation.
>
> But what can be done if fsync returns before pages flushed?
Just what Tom has done: preserve a little more history. If it's not
too expensive, then it doesn't hurt you when running on sound hardware,
but it offers a good chance of preventing embarrassments for (the
overwhelming fraction of) users on garbage hardware.
Nathan Myers
ncm@zembu.com