Copying files fast between two machines


The quick way

The quickest way to transfer files over a LAN is likely not rsync, unless there are few changes. rsync spends a fair bit of time doing checksums, calculating differences, etc. If you know that you're going to be transferring most of the data anyway, just do something like this (note: there are multiple implementations of netcat; check the manual for the correct options. In particular, yours might not want the -p):

[email protected]:/target$ nc -q 1 -l -p 1234 | tar xv

[email protected]:/source$ tar cv . | nc -q 1 dest-ip 1234

That uses netcat (nc) to send tar over a raw TCP connection on port 1234. There is no encryption, authenticity checking, etc, so its very fast. If your cross-connect is running at gigabit or less, you'll peg the network; if its more, you'll peg the disk (unless you have a storage array, or fast disk). The v flags to tar make it print file names as it goes (verbose mode). With large files, that's practically no overhead. If you were doing tons of small files, you'd turn that off. Also, you can insert something like pv into the pipeline to get a progress indicator:

[email protected]:/target$ nc -q 1 -l -p 1234 | pv -pterb -s 100G | tar xv

You can of course insert other things too, like gzip -1 (and add the z flag on the receiving end—the z flag on the sending end would use a higher compression level than 1, unless you set the GZIP environment variable, of course). Though gzip will probably actually be slower, unless your data really compresses.

Posted on: Sunday 21 May 2017