On Thursday 20 November 2008 00:30, Per Jessen wrote:
Randall R Schulz wrote:
On Wednesday 19 November 2008 10:12, Per Jessen wrote:
dd if=/tmp/file1 of=/tmp/file2 bs=1M
27m28s 13Mb/sec
dd if=/tmp/file1 of=/tmp/file2 bs=1000M
17m34s 20Mb/sec
That's not really a correct computation. Every byte (or sector or whatever) must be read once and written once, and you have to account for both the read and the write traffic.
I didn't compute it, I was just quoting from the dd output.
Yes, but dd is only telling you its throughput. Getting the correct I/O device throughput requires that you know things that dd does not about where the data is coming from and going to. In this case, you know the input and the output both originate and terminate in the same disk drive, so that drive (and the buss that connects it to its controller) are serving both the read and the write traffic. So unless you account for this, you're underestimating the device (and buss and controller) throughput by a factor of two.
/Per
Randall Schulz -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org