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Re: ahcisata poor performance

On Mon, Jul 14, 2014 at 12:37:09PM +0200, Manuel Bouyer wrote:
> On Mon, Jul 14, 2014 at 02:38:14AM +0400, Dima Veselov wrote:
> > Hello!
> > 
> > Can someone tell - is there a way to inspect poor hard drive performance?
> > 
> > Two computers - windows and linux, SMB and NFS connected to NetBSD host.
> > 
> > Writing over SMB (GE interface) freeze linux NFS client (writing few bytes
> > can take 2 seconds).
> > 
> > I believe thats hard drive problem because iostat show not more than 10MB/s
> > even copying locally on NetBSD from one drive to another. Top show up to
> > 10% interrupt.

By 'hard disk problem' I had in mind 'not network'. dd benchmarking prove that.

> I would try some benchmark like iozone.

Don't know if I interpret iozone data correctly, but there is a significant
loose of writing speed at 32k (and bigger) blocks, comparing to 16k or 
smaller. It is seen on write, rewrite, fwrite, frewrite columns. I'm in 
doubt, because i don't beleive in 800Mb/s or 1Gb/s speed of fwrite (for 
less than 16k), however 17-20 Mb/s (for 32kb and more) look quite real.

The original question was about - how to know where speed loses?

> A simple dd from /dev/zero can also give some information:
> dd if=/dev/zero of=file bs=1m count=50000
> (you have to make sure the file created doesn't fit in ram).

Stats are awful.

Linux/amd64 on usual workstation computer gave 111Mb/s

NetBSD 6.0/amd64 (with RAIDframe) Intel 82801JI SATA Controller
Intel Xeon E5506 working good as server 54.5 Mb/s

NetBSD 6.1.4/amd64 which was originally discussed
RAIDframe dk-raid-dk sandwitch
AMD Athlon(tm) 7750 Dual-Core Processor
NVIDIA nForce MCP77 ATA133 IDE Controller gave 13Mb/s

> Also you don't say what kind of access you're doing: a single large
> file write, or lots of small files ?

Don't see much difference. I would say big files make it freeze more,
but maybe it just because of little breathes between small ones? :)

Iozone don't load much - it take 2-10% CPU and not more than 1%
interrupt, but samba bigfile copy take 6% CPU and up to 10% int.

Anyway saving this message during iozone make me feel the problem
(1-2 seconds of freeze while saving).

One more thing - this system previously worked with NetBSD 5 for
years and I never noticed anything like that. Hardware was the
same except it was 1x1Tb Raidframe disk instead of 2x3Tb now.

Sincerelly yours

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