Windows – How to mirror a folder (copy only missing and changed files recursively) in windows

There's a few ways to do this;

1.) DFS folder replication will work, there's a tutorial here and here's the MS webpage.

2.) Robocopy in mirroring mode will work as well, but it won't key off the fact that a file has changed. Here's a script that I shamelessly copied from somewhere, (why re-invent the wheel, eh? :) that I used when migrating large amounts of data from one share to another. (A big bonus with this is that it will do incremental mirroring, i.e. run it once to replicate, then run it again and it will only copy over the files that have changed.

Script is:

@ECHO OFF
SETLOCAL

SET _source="\workstation01\share"

SET _dest="\workstation02\share"

SET _what=/COPYALL /B /SEC /MIR
:: /COPYALL :: COPY ALL file info
:: /B :: copy files in Backup mode.
:: /SEC :: copy files with SECurity
:: /MIR :: MIRror a directory tree

SET _options=/R:0 /W:0 /LOG:worstation_copy.txt /NFL /NDL
:: /R:n :: number of Retries
:: /W:n :: Wait time between retries
:: /LOG :: Output log file
:: /NFL :: No file logging
:: /NDL :: No dir logging

ROBOCOPY %_source% %_dest% %_what% %_options%

3.) If you use HP in a large corporate setting and have a vendor agreement or something set up with them, check into HP StorageWorks Storage Mirroring, however it's a bit heavy-handed for two windows folders.

4.) Finally, there's also, (beta warning! Beta warning!) Windows Live Mesh, but it's.. You know, beta. :)

Personally, I'd go with the robocopy option.

From a performance standpoint only, xcopy or robocopy will give you similar results. I ran through a couple of tests on a Windows Vista 64-bit SP2 box to do some comparisons. All copies were performed between a internal 7200 RPM Sata II disk and an external USB 2.0 drive or on the same internal drive itself where indicated. No special setup was done (make up your own mind if that invalidates/validates the test), only to input the command into a batch file to execute. PowerShell was used to capture the start and stop times. After a couple of passes here are the averages from the tools I played with:

File: 732,909,568 bytes (698 MB), 1 ISO file copied to different directory on the same internal disk.

copy      6 secs (ex. copy G:\folder1\* G:\folder2\)
xcopy     6 secs (ex. xcopy G:\folder1 G:\folder2 /I /E /Y /R)
robocopy  6 secs (ex. robocopy G:\folder1\ G:\folder2 /E /NP)
teracopy 28 secs (ex. TeraCopy.exe Copy G:\folder1\ G:\folder2\)
fastcopy 19 secs (ex. fastcopy.exe /auto_close G:\folder1 /to=G:\folder2)  

File: 732,909,568 bytes (698 MB), 1 ISO file copied to external USB disk.

copy     36 secs (ex. copy G:\folder1\* I:\folder2\)
xcopy    35 secs (ex. xcopy G:\folder1 I:\folder2 /I /E /Y /R)
robocopy 36 secs (ex. robocopy G:\folder1\ I:\folder2 /E /NP)
teracopy 36 secs (ex. TeraCopy.exe Copy G:\folder1\ I:\folder2\)
fastcopy 38 secs (ex. fastcopy.exe /auto_close G:\folder1 /to=I:\folder2)  

Files: 45,039,616bytes (42.9MB) 5 random files copied to external usb disk

copy      6 secs (ex. copy G:\folder1\* I:\folder2\)
xcopy     5 secs (ex. xcopy G:\folder1 I:\folder2 /I /E /Y /R)
robocopy  6 secs (ex. robocopy G:\folder1\ I:\folder2 /E /NP)
teracopy 12 secs (ex. TeraCopy.exe Copy G:\folder1\ I:\folder2\)
fastcopy  6 secs (ex. fastcopy.exe /auto_close G:\folder1 /to=I:\folder2)

Files/directoies: 1,087,180,800 bytes (1.01 GB), 27 files/8 directories copied to external USB disk.

copy     *Not included in test
xcopy    57 secs (ex. xcopy G:\folder1 I:\folder2 /I /E /Y /R)
robocopy 58 secs (ex. robocopy G:\folder1\ I:\folder2 /E /NP)
teracopy 56 secs (ex. TeraCopy.exe Copy G:\folder1\ I:\folder2\)
fastcopy 60 secs (ex. fastcopy.exe /auto_close G:\folder1 /to=I:\folder2)

This is by no means an exhaustive test, but just throwing a quick real world scenario at some of the more popular tools in this genre shows that your pretty safe sticking with either xcopy or Robocopy (from a performance standpoint only). Also the Robocopy option /NP (No Progress) saves you 0 time. That doesn't mean you cannot benefit from using something other than xcopy however. Robocopy is a great example (from Wikipedia):

Robocopy is notable for capabilities above and beyond the built-in Windows copy and
xcopy commands, including the following:

• Ability to tolerate network outages and resume copying where it previously left off (incomplete files are noted with a date stamp corresponding to 1980-01-01 and contain a recovery record so Robocopy knows from where to continue).
• Ability to correctly copy attributes, owner information, alternate data streams, auditing information, and timestamps by default, without the need for numerous often forgotten command line switches.
• Ability to correctly copy NTFS ACLs, (when /COPYALL provided), and to assert the Windows NT "backup right" (/B) so an administrator may copy an entire directory, including files denied readability to the administrator.
• Persistence by default, with a programmable number of automatic retries if a file cannot be opened.
• A "mirror" mode, which keeps trees in sync by optionally deleting files out of the destination that are no longer present in the source.
• Ability to copy large numbers of files that would otherwise crash the built-in XCOPY utility.
• A progress indicator on the command line that updates continuously.
• Ability to copy long file and folder names exceeding 256 characters — up to a theoretical 32,000 characters — without errors.