On Mon, 2010-07-19 at 17:40 -0700, Chad Cantwell wrote:
> fyi, everyone, I have some more info here. in short, rich lowe's 142 works
> correctly (fast) on my hardware, while both my compilations (snv 143, snv 144)
> and also the nexanta 3 rc2 kernel (134 with backports) are horribly slow.
The idea that its a regression introduced into NCP 3RC2 is not very far
fetched at all.
It certainly could stand some more analysis.
- Garrett
>
> I finally got around to trying rich lowe's snv 142 compilation in place of
> my own compilation of 143 (and later 144, not mentioned below), and unlike
> my own two compilations, his works very fast again on my same zpool (
> scrubbing avg increased from low 100s to over 400 MB/s within a few
> minutes after booting into this copy of 142. I should note that since
> my original message, I also tried booting from a Nexanta Core 3.0 RC2 ISO
> after realizing it had zpool 26 support backported into 134 and was in
> fact able to read my zpool despite upgrading the version. Running a
> scrub from the F2 shell on the Nexanta CD was also slow scrubbing, just
> like the 143 and 144 that I compiled. So, there seem to be two possibilities.
> Either (and this seems unlikely) there is a problem introduced post-142 which
> slows things down, and it occured in 143, 144, and was brought back to 134
> with Nexanta's backports, or else (more likely) there is something different
> or wrong with how I'm compiling the kernel that makes the hardware not
> perform up to its specifications with a zpool, and possibly the Nexanta 3
> RC2 ISO has the same problem as my own compilations.
>
> Chad
>
> On Tue, Jul 06, 2010 at 03:08:50PM -0700, Chad Cantwell wrote:
> > Hi all,
> >
> > I've noticed something strange in the throughput in my zpool between
> > different snv builds, and I'm not sure if it's an inherent difference
> > in the build or a kernel parameter that is different in the builds.
> > I've setup two similiar machines and this happens with both of them.
> > Each system has 16 2TB Samsung HD203WI drives (total) directly connected
> > to two LSI 3081E-R 1068e cards with IT firmware in one raidz3 vdev.
> >
> > In both computers, after a fresh installation of snv 134, the throughput
> > is a maximum of about 300 MB/s during scrub or something like
> > "dd if=/dev/zero bs=1024k of=bigfile".
> >
> > If I bfu to snv 138, I then get throughput of about 700 MB/s with both
> > scrub or a single thread dd.
> >
> > I assumed at first this was some sort of bug or regression in 134 that
> > made it slow. However, I've now tested also from the fresh 134
> > installation, compiling the OS/Net build 143 from the mercurial
> > repository and booting into it, after which the dd throughput is still
> > only about 300 MB/s just like snv 134. The scrub throughput in 143
> > is even slower, rarely surpassing 150 MB/s. I wonder if the scrubbing
> > being extra slow here is related to the additional statistics displayed
> > during the scrub that didn't used to be shown.
> >
> > Is there some kind of debug option that might be enabled in the 134 build
> > and persist if I compile snv 143 which would be off if I installed a 138
> > through bfu? If not, it makes me think that the bfu to 138 is changing
> > the configuration somewhere to make it faster rather than fixing a bug or
> > being a debug flag on or off. Does anyone have any idea what might be
> > happening? One thing I haven't tried is bfu'ing to 138, and from this
> > faster working snv 138 installing the snv 143 build, which may possibly
> > create a 143 that performs faster if it's simply a configuration parameter.
> > I'm not sure offhand if installing source-compiled ON builds from a bfu'd
> > rpool is supported, although I suppose it's simple enough to try.
> >
> > Thanks,
> > Chad Cantwell
> > _______________________________________________
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