Re: Disk performance under CURRENT

On Sat, May 22, 2004 at 09:46:11AM +0200, Poul-Henning Kamp wrote:
> In message <20040521224729.680285D0A_at_ptavv.es.net>, "Kevin Oberman" writes:
> >I just ran test of disk writing performance under V4 (STABLE) and V5
> >(CURRENT) and was surprised at the difference.
> >
> >The test was simple and not at all rigorous. Just a dd bs=256k
> >if=/dev/zero of=/dev/ad2. This is about the simplest way of dealing with
> >a disk. No file system or anything else. Just raw data to the device.
> >
> >Under STABLE, I get an average of 25 MB/sec to the disk. Under CURRENT,
> >it drops to 15 MB/sec. I did this because I had noted that it was now
> >taking over an hour to backup my system disk (40 GB) when it was only
> >taking 40 minutes when I was running V4.6. The STABLE system was built
> >yesterday. The CURRENT system last Sunday.
> >
> >Any idea why this is so much slower? It looks to me like it must be in
> >either geom or the disk driver.
> 
> GEOM is slower than 4-stable in a degenerate case like this, but it
> sounds to me like there is something else involved here too.  Have
> you removed WITNESS from your kernel ?

Yeah, perhaps something else like using /dev/ad2 which is a bdev in
-STABLE but cdev in -CURRENT?

-- 
Brian Fundakowski Feldman                           \'[ FreeBSD ]''''''''''\
  <> green_at_FreeBSD.org                               \  The Power to Serve! \
 Opinions expressed are my own.                       \,,,,,,,,,,,,,,,,,,,,,,\