On Fri, 27 Aug 2010, Adam Morris wrote: > On Fri, Aug 27, 2010 at 03:00:53PM -0500, Mike Miller wrote: > >> Related question: I'm pretty sure there's a way to pipe the stdout to >> ssh and have it transfer to /dev/null on the other end so that you can >> compare speeds for arbitrarily large transfers without making files. >> Anyone know? >> >> dd if=/dev/zero bs=1024k count=4000 | ssh ... >> >> I think if you were to make your file much bigger, maybe several >> gigabytes, you'd see a big benefit of compression. It's not a >> realistic example though because your file is just the same null >> character repeated a gazillion times. So, on your network, running at >> 250 Mbps or so, you probably never want to use compression. > > I believe that copying to /dev/null would go so quickly that it wouldn't > be a valid test. I don't mean to copy to /dev/null on the same machine. I mean that you generate data using dd and /dev/zero on one machine, send that to stdout, catch it with ssh and send it to a second machine where it is received into /dev/null on that machine. That is without compression. The second test does the same thing except that it uses ssh with -C option. For a third comparison you could use gzip -c on the sending machine and gunzip -c on the receiving machine. The idea is to test the transfer speed for gigabytes of data without having to use any HDD space. Mike