> -- [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