Date: Sat, 6 Nov 1999 05:48:38 -0600 From: Rob Snow <RSnow@lgc.com> To: John-Mark Gurney <gurney_j@resnet.uoregon.edu> Cc: freebsd-questions@freebsd.org Subject: RE: writing much slower than reading... Message-ID: <9F147E391A3FD111B9A800805F356C52E25974@lgcadev001.zycor.lgc.com>
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Wow, I'm impressed! I bought the 10.1G 7200 last year for my Linux box, and
I thought it was fast! Do me a favor, run Bonnie on it, with a 256M file. (
bonnie -s 256 )
Bonnie is in ports/benchmarks.
Now, on to your problem, am I reading something wrong? It looks like your
numbers are within 10% of each other.
-Rob
-----Original Message-----
From: John-Mark Gurney [mailto:gurney_j@efn.org]
Sent: Saturday, November 06, 1999 5:32 AM
To: Rob Snow
Cc: freebsd-questions@freebsd.org
Subject: Re: writing much slower than reading...
Rob Snow scribbled this message on Nov 6:
> Emm, I want your system. Have you double checked your numbers? They
> look a bit high. Here's what I get on a vinum stripe across two 'cudas
> on an SMP box:
go to IBM's web site and read about the drive... I bought the drive
for $241 at gogocity.com... it's a 27gig 7200rpm drive, and IBM
advertises that the platter speed is 13.8meg/sec to 22meg/sec... the
performance is the main reason that I bought the drive... :)
also, don't forget I'm using the raw device, so there isn't any buffer
like if I was going through the file system...
just so you know, I went and grabed rawio to run on the disk:
$ rawio -c 128 -r -w /dev/rwd0s1g
Random read Sequential read Random write Sequential write
ID K/sec /sec K/sec /sec K/sec /sec K/sec /sec
anon 29293.9 447 28755.4 439
the -c 128 sets it for 64k transfers, and by default does 16384
transfers, so we were transfering 1gig of data... the raw partition
is actually a couple gigs into the drive... and is ~25gigs large...
> rsnow@basil% time dd if=/dev/vinum/rstripe of=/dev/null bs=64k
> count=2048
> 2048+0 records in
> 2048+0 records out
> 134217728 bytes transferred in 7.938773 secs (16906609 bytes/sec)
> 0.007u 0.520s 0:07.98 6.5% 73+371k 2+0io 0pf+0w
> John-Mark Gurney wrote:
> >
> > well, I am working on writing a capture program to do
640x480x12bpp@30fps
> > to a raw disk, but writing to the raw device is SOOO slow... the reason
> > I say it's slow is the fact that it takes 8 times the system time
writing
> > than reading...
> >
> > a bit about the system... k6/2-250, 100mhz system bus, pc100 64meg
dimm,
> > VIA MVP3 chipset (IDE DMA enabled), IBM-DPTA-372730 hard disk, Hauppauge
> > WinCast/TV Model 61351 B226, 3.3-RELEASE...
> >
> > now the hard disk can push and pull around 20meg/sec w/o any problems..
> > but when I time the disk I get:
> > $ time dd if=/dev/rwd0s1g of=/dev/null bs=64k count=2048
> > 2048+0 records in
> > 2048+0 records out
> > 134217728 bytes transferred in 5.747521 secs (23352281 bytes/sec)
> > 5.75 real 0.01 user 0.21 sys
> > $ time dd if=/dev/zero of=/dev/rwd0s1g bs=64k count=2048
> > 2048+0 records in
> > 2048+0 records out
> > 134217728 bytes transferred in 6.281820 secs (21366057 bytes/sec)
> > 6.28 real 0.00 user 1.68 sys
> >
> > now, why does it cost SOOO much more processing time to write than
> > read?? are there plans to fix this slow down? is it possible? can't
> > we just dma write out of userland since we are blocking on the write?
--
John-Mark Gurney Voice: +1 408 975 9651
Cu Networking
"The soul contains in itself the event that shall presently befall it.
The event is only the actualizing of its thought." -- Ralph Waldo Emerson
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