On Sat, 28 Apr 2001, Bruce Evans wrote:
> On Fri, 27 Apr 2001, Cejka Rudolf wrote:
> > Right now, I have upgraded my -current machine from
> > February 13 to April 26.
> > I were pleased with change to dir allocation in FFS,
> > but here are my unpleasant test results (UDMA33, partition
> > is 3 GB where 1 GB is free, soft-updates are enabled):
> > ...
> > rm -r is much faster, but tar xvfz is much slower.
> This is probably caused by write caching now being off by default
> in the ata driver, possibly amplified by not using soft updates.
> Without the new dir allocation, -current would be even slower :(.
> This is also probably caused by write caching not being done.
For the people wanting to turn on write caching ... it WILL break
the write ordering needed by softupdates and journaling filesystems,
so don't do it unless you know what you're doing.
I guess it would be better to do this kind of write caching at the
kernel level, because the OS has a much better idea of when to write
which data to platter than a harddisk can ever have.
OTOH, note that switching off write caching on some drive doesn't
actually work because the manufacturers would rather do well on some
PC mag benchmarks than store your data reliably ...
Virtual memory is like a game you can't win;
However, without VM there's truly nothing to lose...
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