> Paul van der Zwan wrote...
> >
> > I am having some performance problems on my -current ( update last weekend)
> > I hooked up a new Seagate ST36530N yesterday ( connected to an Adaptec
> > 2940U)
> Andreas Klemm has had similar trouble, as he pointed out.
> Can you check and see whether or not you have write caching turned on for
> your disk? I have seen problems with sequential writes that appear to be
> caused by conflicts between FreeBSD's caching policy and disk caching
> policies. These problems often go away when you disable write caching on a
> disk.
>
> The Write Cache Enable (WCE) bit is in mode page 8. To check it:
>
> camcontrol modepage -n da -u 1 -v -m 8
>
> To edit the mode page:
>
> camcontrol modepage -n da -u 1 -v -m 8 -e
>
> Let me know whether that affects the problem at all.
This did not improve anything , but I think I have found the couse.
In that modepage there is a DISC value which was 0 on the IBM and 1 on the
Seagate. I remembered a ' Enable disconnect' option in the Adaptec 2940 bios,
setting this to 'off' for both harddisks led to a huge performance increase on
the Seagate. If I also enable Ultra mode iozone write goes from 1.5 MB/s
to 12 MB/s ( a factor of 8 !!!).
Paul
--
Paul van der Zwan paulz @ trantor.xs4all.nl
"I think I'll move to theory, everything works in theory..."
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