On Thu, 31 Dec 2009 19:57 +0100, "Tomas Bodzar" <tomas.bod...@gmail.com> wrote: > I tried it in VM on VirtualBox. Here is my output : > > $ dd if=/dev/rwd0c of=/dev/null bs=1m count=10 > 10+0 records in > 10+0 records out > 10485760 bytes transferred in 0.403 secs (25985597 bytes/sec) > $ > > $ dd if=/dev/rwd0c of=/dev/null > ^C18777+0 records in > 18777+0 records out > 9613824 bytes transferred in 8.291 secs (1159492 bytes/sec) > $ > > See difference in speed. So it looks like it's really good idea to use > bs and count options.
My earlier suggestion of bs=4m is probably way too large. After 64k, it doesn't get much faster... at least on my USB drives: # time dd if=/dev/rsd1c of=/dev/null bs=64k 3859+1 records in 3859+1 records out 252968448 bytes transferred in 23.163 secs (10920945 bytes/sec) 0m23.16s real 0m0.00s user 0m0.00s system