Re: [POT] Which journalised filesystem ?

Pavel Machek
2001-10-06T20:18:34Z

Hi!

> > > > We (as in Linux) should make sure that we explicitly tell the disk when
> > > > we need it to flush its disk buffers. We don't do that right, and
> > > > because of _our_ problems some people claim that writeback caching is
> > > > evil and bad.
> > >
> > > Does this even work right for IDE ?
> >
> > Current IDE drives it may be a NOP. Worse than that it would totally ruin
> > high end raid performance. We need to pass write barriers. A good i2o card
> > might have 256Mb of writeback cache that we want to avoid flushing - because
> > it is battery backed and can be ordered.
>
> If the cache is small and is primarily a track cache (IDE) one trick that
> we can do is to flood the cache with data so everything is forced out.
>
> We can do this at mkfs time, (so even destructive tests are allowed)
> and we can probe how to make this work for a particular drive. And
> then the kernel can just use the results of that probe.

How do you probe this without actually powering system down?