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Re: ahcisata poor performance


Sorry, I have lost your last message, but wish to know something about
4k-alignment. What should be aligned to what?

I assume sector is 512-byte and gpt show it in sectors. So I have
gpt disk part 5801288527 sectors, it doesn't align to anything.

raidctl says it in sectors too and size is 5801288448, so it is aligned
to 4k, and is aligned to sectPerSU, which is 128 blocks.

dk10 is 5801288381, which is aligned to nothing too, filesystem resides
on this wedge seem to be unaligned. It is the only thing I have to do is
to shrink filesystem to align to 4k blocks? Or better align it to 128*512 to
match raid somehow? Or I have to rebuild wedges to align to something?

Or maybe I am completely wrong and all the things should be aligned not
only by its size but also by its start?

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.
> I would try some benchmark like iozone.
> 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).
> Also you don't say what kind of access you're doing: a single large
> file write, or lots of small files ?
> -- 
> Manuel Bouyer <>
>      NetBSD: 26 ans d'experience feront toujours la difference
> --

Sincerelly yours

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