zfs very poor performance compared to ufs due to lack of cache?

[Kostik Belousov]

On Mon, Sep 06, 2010 at 01:54:15PM +0300, Andriy Gapon wrote:
> on 06/09/2010 02:57 Steven Hartland said the following:
> > Based on Jeremy's comments I'm updating the box the stable. Its building now
> > but will be the morning before I can reboot to activate changes as I need to
> > deactivate the stream instance and wait for all active connections to finish.
> > 
> > That said the problem doesn't seem to be cache + free but more cache + free
> > + inactive with inactive being the large chunk, so not sure this change
> > would make any difference?
> > 
> > How does ufs deal with this, does it take inactive into account? Seems a bit
> > silly for inactive pages to prevent reuse for extended periods when the
> > memory could be better used as cache.
> 
> Inactive pages are also a cache, just a different kind.
Not quite. Inactive pages may be dirty. Such pages cannot be freed or reused
without pageout.
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