Date: Mon, 3 Jul 2000 12:36:02 +0400 (MSD) From: kostik <kostik@org.chem.msu.su> To: Kent Stewart <kstewart@3-cities.com> Cc: David Gilbert <dgilbert@velocet.ca>, freebsd-stable@freebsd.org Subject: Re: Dump takes ages on SCSI. (several times faster on IDE) Message-ID: <Pine.BSF.4.05.10007031229260.39542-100000@org.chem.msu.su> In-Reply-To: <395FF18D.6B47A620@3-cities.com>
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On Sun, 2 Jul 2000, Kent Stewart wrote:
> > >>>>> "Kent" == Kent Stewart <kstewart@3-cities.com> writes:
> >
> > >> I then noticed that the IDE would crashdump somewhere around 10
> > >> times faster than the SCSI disk.
> > >>
> > >> Why? Can the SCSI speed be improved?
> >
> > Kent> It depends on what 2940 and what IDE drive you are talking
> > Kent> about. I have a Maxtor UDMA66 that is 20MB/s faster in some
> >
> > I don't think this explains it at all. It would appear that the SCSI
> > driver is running in some "extra safe" mode, or something. It has
> > 512M to write sequentually to a partition... and the counting on the
> > screen, we're looking at 2 to 3 seconds-per-megabyte (on a drive that
> > delivers write performance of about 10M/s in normal operation).
> >
> > Maybe what I should have said that the ratio of regular operation to
> > dump performance of the ide driver is about 1:1 while it's 10:1 for
> > the SCSI driver... why is this?
>
> I don't have any idea up front. One thing comes to mind and that is
> does your Quantum come up with "tagged queuing enabled". My IBM has
i have the same hdd, ibm dcas-34330W.
it is very interesting that "tagged queuing" was enabled for scsi driver
while i was working with freebsd-3.0-release
and became disabled (or isn't recognised) when i upgrade to
freebsd-4.0-release.
> that disabled or more precisely never enabled, which makes it slower
> and safer. My dmesg shows the drive as
>
> da0: <IBM DCAS-34330W S65A> Fixed Direct Access SCSI-2 device
> da0: 40.000MB/s transfers (20.000MHz, offset 8, 16bit)
> da0: 4134MB (8467200 512 byte sectors: 255H 63S/T 527C)
>
can you explain me this "safeness" please ?
WBR, Konstantin Yu. Pasichnichenko
E-mail : kostik@org.chem.msu.su
FIDO : 2:5020/118.82@fidonet.org
p.s. sorry my bad english.
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