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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