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Asked: 2009-07-28 10:41:12 +0800 CST

How do you limit the bandwidth for a file copy?

  • 772

I've got an old windows 2000 box in a remote location with a T1 connection and a vpn to my location. I normally use smb mounts to transfer files but now it's time to decommission the server and copy it's backups to my location. I have about 40 gigabytes (compressed) to copy. I'm prepared for it to take a long time, but I have a few caveats.

  • I need to limit the bandwidth so terminal service connections to the site are not affected
  • I want to be able to resume a partial transfer

There are a few small files and several large files (10-20 gigabytes). I'm familiar with rsync on *nix platforms but have had bad luck with windows and I don't know that it will really keep partially transfered files. What do you use?

backup windows-server-2000 file-transfer

6 Answers

  1. Best Answer

    robocopy.exe has a switch called inter-packet gap, allowing you to insert a time window in between the packets of your copy, and thereby reduce the impact on the channel.

    It's not exactly "use no more than 30% of the available bandwidth", but you can acheive the same effect with a little math. You can always specify some number of milliseconds and let it run for a bit, then CTRL+C to interrupt, adjust your command as needed, then resume. I've done just this when I didn't want to overload the WAN during the business day with massive replications.

    robocopy has another switch /z allowing for "resumeable" transfers, so if the transfer is interrupted you can pick up where you left off, and don't need to shift the whole 40 GB again.

    I'm not sure how granular the resume bit is, because I've never really tested for example a single 40GB ZIP file. Test something smaller first ;-)

    There are some nice GUIs for robocopy which can assist with the syntax, but anyone with a Linux background will grok it easily. Grab the latest versions from a copy of Windows 2003 or later. Otherwise you'll find it as a Windows 2000 Resource Kit Tool download.

    In the Wikipedia entry for robocopy, someone noted that the penalty for restartable copying (the /z switch) is 6x slower performance (see Known Flaws).

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  2. 40 GB of files are going to take more than 60 hours to copy over a T-1. It might be easier to mail an external hard drive in both directions. You can have someone plug it into the server, copy/encrypt your files and then have them mail it back to you.

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  3. You could try setting up FTP on the 2000 box, and using a FTP client at the other end, like filezilla to deal with partial copies.

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  4. You say you've used rsync on *nix, there are several ports of rsync to windows you might look into. For example:

    Personally I've found rsync pretty reliable, and it can handle interruptions in the middle of transfers and so on. Rsync also has a flag to limit transfers to an exact kbit/sec transfer speed, so that would seem to work for you as well.

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  5. I use Robocopy to back up all of my servers as well as a live Mailserver backup. Once it is set up right, its truly set it and forget it. Best thing that ever happened to my IT life. Just putting in my 32 cents (allowing for inflation)

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  6. I use KillCopy for this purpose. I find it very convenient.
    It has separate speed and other settings profiles for local and network copy.
    It is also able to resume when a transfer of a large file (or files) is interrupted in case of bad connection, or even when the computer hosting the program crashes.

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