Re: Some comments on ZFS

On Tuesday 17 April 2007 22:37, Thomas Sparrevohn wrote:
> On Tuesday 17 April 2007 12:43:13 Gary Jennejohn wrote:
> > Robert Watson writes:
> >
> > Interestingly enough, I see less memory pressure since switching to
> > ZFS. But I'm not using RAIDZ. Previously ``make buildworld'' would
> > use much more memory, probably for buffer caching. It looks like ZFS
> > doesn't use nearly as much buffer cache as UFS (which may not be a
> > good thing).
>
> On this system 4GB system - 2,3GB available - ZFS stops around
> 1,3GB Free whereas UFS continues until app. 700MB mark on a
> buildworld
>
> But the price seems to be much more disk activity - Given that
> the difference - after disabling Witness - was
>
> UFS 10m32.10s real          27m1.32s user           7m49.01s sys    
> (Systat 700MB Free) ZFS  17m43.66s real          27m30.70s user        
>  17m28.47s sys  (Systat 1,3GB Free)
>
> It make me think that ZFS is trading memory for performance - my guess
> is - that given the same memory usage ZFS would be unbeatable - I must
> say that Pawel has done a great job porting ZFS

I have reverted the 3/4 -> 1/2 arc size limit locally, which gives better 
results in my test: playing hd video off the same disk while doing a 
(single threaded) buildworld from the same zpool (single disk, no mirror, 
no raidz).  With the 1/2 limit, I get frequent hick-ups in the playback - 
while with 3/4 things run (almost) smoothly.

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