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How would you backup 600+ GB of data on a NAS (Network-Attached Storage) drive to a USB external drive?

The NAS drive does not contain mission critical data nonetheless I wish to make weekly copies of it just in case. The NAS drive is almost exclusively used as an archive dump and is rarely updated. However the backup strategy used must have a simple restore procedure so I can confidently say the data now on the NAS drive is exactly how it was at the time of backup.

I did try xcopy but seemed like it would take many-many hours and eventually crashed with insufficient memory. suggests I would need to use xxcopy instead due to folder/file name lengths. My concern with xcopy/xxcopy is the length of time it takes. Hoping something else is faster.

  • NAS drive is DLink DNS-313. 1TB drive installed. Connected to router via Ethernet cable.
  • USB drive is Seagate 1TB. Can be connected to Windows Vista (preferred) or Windows 7 PCs. Both PCs are usually connected Wirelessly however ethernet cable can be used during backup to speed up the process.
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not sure if you can just plug the usb drive into the back nas device, it looks like it might have the capability to do this! – user33788 Jun 8 '10 at 5:06
@smokenheap. The DLink DNS-313 can be attached via Ethernet or USB but does not allow piggy backing as you suggest. – Tim Murphy Jun 9 '10 at 21:10

I use rsync (under Cygwin) to do this.

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up vote 2 down vote accepted

I've done a reasonable amount of research on the issue and have decided to go with robocopy.

Why did I choose robocopy:

  • Already installed on Windows Vista/7.
  • Command line so easy to configure for batch file.
  • Logging and output to console.
  • Handles path names greater than 260 characters.

To create the first backup I used the DLink DNS-313's USB port with the following command:

robocopy G:\Data F:\Data /e /dcopy:T /xj /log:BackupNAS-2008.log /tee /v /np
  • Source folder G:\Data
  • Destination folder F:\Data
  • /e Copies subdirectories. Note that this option includes empty directories.
  • /dcopy:T Copies directory time stamps.
  • /xj Excludes junction points, which are normally included by default.
  • /log:BackupNAS-2008.log Writes the status output to the log file (overwrites the existing log file).
  • /v Produces verbose output, and shows all skipped files.
  • /np Specifies that the progress of the copying operation (the number of files or directories copied so far) will not be displayed.

/np switch is very important if you are using the /log switch. Without /np the log file will be cluttered with each % up robocopy displays to the console. This is a real shame and quite frankly stupid.

After approximately 9 hours of copying (remember I have approximately 450GB to copy) and best I can tell 90% complete Windows Update kicked in and decided to reboot my machine. No problems I just ran the same command again and robocopy compares the two directories (and sub-directories) and only copies what is missing/different.

After reinstalling the DNS-313 as a network drive the command line will change to:

robocopy \\nas-313\Data F:\Data /e /dcopy:T /xj /log:BackupNAS-2008.log /tee /v /np /purge /z

The new switches are:

  • /z Copies files in Restart mode. This is a good switch to use when copying across a network as it will handle any network interruptions.
  • /purge Deletes destination files and directories that no longer exist in the source. /e /purge can be replaced with /mir.


The only real negative so far is the log file. It provides the required information but it is not very well laid out. I think they would have been better using a standard log file format then you could easily import it into a database/excel for review.


To improve USB external drive performance turn on write caching.

Other Products

  • @Mike Fitzpatick suggested rsync. I didn't try it as its history is with linux and I often find documentation for linux programs lacking.
  • robocopy does have a GUI via RichCopy.
  • SyncToy. Tried it. Looks good but it would say there were errors but not probably describe what they were.
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