> -- [EMAIL PROTECTED]: ~ (17:39) --
> # dd if=/dev/wd0c of=/dev/null bs=819200 count=20
> 20+0 records in
> 20+0 records out
> 16384000 bytes transferred in 0.711 secs (23012820 bytes/sec)
>
>
> recall the old speed with apm0: -
>
> -- [EMAIL PROTECTED]: ~ (17:13) --
> # dd if=/dev/wd0c of=/dev/null bs=819200 count=20
> 20+0 records in
> 20+0 records out
> 16384000 bytes transferred in 1.129 secs (14509606 bytes/sec)
>
> that's pretty harsh if other people can reproduce it. :(
>
>
> Incidentally usb transfers *weren't* improved by removing apm0 -
>
> -- [EMAIL PROTECTED]: ~ (17:39) --
> # dd if=/dev/sd0c of=/dev/null bs=819200 count=20
> 20+0 records in
> 20+0 records out
> 16384000 bytes transferred in 6.017 secs (2722653 bytes/sec)
>
> so there's some other factor limiting those.
>
I'm getting the same speed on a snapshot from 09/21 with amd64 on a brand new
amd 64 3800+.
Lately I was copying around 40G of data onto a usb 2.0 hard disk (yes it was
attached to EHCI) and wondered why it took so long, but I didn't pursue the
issue further.
I also tried with different blocksizes and to eliminate the issue of a too
short benchmark I ran for a couple of minutes (about count=500).
Actually .... wait a minute ... /dev/sd0c and /dev/wd0c ?
Are you SUPPOSED to read of a block device ?
SHOULDN'T it be /dev/rsd0c and /dev/rwd0c ???
^ ^ RAW
DEVICE
With the raw devices the speed looks QUITE different:
BLOCK DEVICE:
sudo dd if=/dev/wd0c of=/dev/null bs=512k count=500
500+0 records in
500+0 records out
262144000 bytes transferred in 16.957 secs (15458831 bytes/sec)
# Top shows CPU usage as 28.7% system, 27.9% interrupt, 41.9% idle
RAW DEVICE:
sudo dd if=/dev/rwd0c of=/dev/null bs=512k count=200
200+0 records in
200+0 records out
104857600 bytes transferred in 1.787 secs (58666485 bytes/sec)
# Top shows CPU usage as 4.6% system, 5.4% interrupt, 90.0% idle
(same with USB device)
BLOCK DEVICE:
sudo dd if=/dev/sd0c of=/dev/null bs=512k count=500
500+0 records in
500+0 records out
262144000 bytes transferred in 96.561 secs (2714791 bytes/sec)
# Top shows CPU usage as 4.7% system, 10.8% interrupt, 84.6% idle
RAW DEVICE:
sudo dd if=/dev/rsd0c of=/dev/null bs=512k count=500
500+0 records in
500+0 records out
262144000 bytes transferred in 19.015 secs (13785462 bytes/sec)
# Top shows CPU usage as 1.6% system, 2.3% interrupt, 96.1% idle
I'm sorry if I understood something wrong, but my understanding was/is that you
only use RAW devices with dd (since it uses it's own "blocks" ).
Please tell me if I'm wrong, since (right) knowledge is valueable!
Regards,
ahb
