Leveraging the Power of the Robocopy /MIR Switch


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In this paper, we explore the idea of using a Robocopy /Mirror Image switch to enable developers to leverage automation and incorporate it into their workflow. To do so, they would need only a Windows PC that has both Robocopy / Mirror Image installed as well as PowerShell (if not already present) and some basic understanding of how each works.

The “robocopy /mir /copyall” is a command-line tool that leverages the power of the Robocopy. The switch allows users to copy all files and subfolders, or only files with a specified extension.

Leveraging the Power of the Robocopy /MIR Switch

Robocopy is a popular tool among system administrators worldwide. RoboCopy is a tried-and-true Swiss army utility for any variety of file transfer situations, with the ability to tackle complicated file transfer operations with ease. For a variety of reasons, synchronizing files is a difficult task. The Robocopy /MIR switch is designed to ease the process of maintaining two folders in sync even simpler. Despite the fact that this switch is not a two-way synchronization, it has a lot of applications!

Check out the Ultimate Guide to Robocopy if you want to learn more about robocopy.

What makes Robocopy /mir so unique?

Assume you have a temporary backup folder and you want to make sure that all of the files in the source directory are copied to the backup directory. Because backup files might be rather huge, we may want to make sure that the destination folder does not fill up with stale backup files too rapidly. Backup folders are often filled with manual backups or temporary copies, and it’s all too simple to run out of storage space.

A copy and purge is the appropriate transfer process to ensure we don’t run out of storage space. This operation ensures that all files in the source directory are copied to the destination directory, as well as removing any destination files that aren’t in the source directory. The Robocopy /mir switch was designed specifically for situations like these!

Robocopy /mir is functionally comparable to Robocopy’s /e /purge options, with a minor variation in behavior. The security settings of a destination directory are not altered when using the /e /purge options. The security settings for the target directory are rewritten when using the /mir option.

If used wrong, /mir, along with a few other commands, may destroy data. Use with care since this has the potential to erase files in the target directory.

Mirror Command for File and Folder Security

As previously noted, security permissions and destination directories behave differently. When using the mirror switch, you may see that just the destination folder permissions are modified, not the file permissions. Individual file permissions were not meant to be duplicated with the mirror command because of performance and practical considerations.

So, how does this work in practice? Let’s look at an example of a source directory folder structure:

  • Folder1
    • File 1 – Permissions that aren’t shared with anybody else
    • File2
  • Folder2 – Permissions that aren’t shared with anybody else
    • File1
    • File2 – Permissions that aren’t shared with anybody else

The following file and folder permission structure is the consequence of a mirror command. The only rights that are passed over are the unique folder permissions, as you can see. The file permissions that are unique to each file will not be passed across.

  • Folder1
  • Folder2 – Permissions that aren’t shared with anybody else

Of fact, there are a variety of instances in which permissions should be replicated and maintained in sync; such cases will be discussed in more depth later in the essay.

In-Practice Use of Robocopy/mir

The Robocopy /mir command may be used in a variety of ways, and specific characteristics have evolved over time. The majority of the changes are to copying file security permissions, which have been simplified in the Vista edition of Robocopy.

To a Destination, Mirror a Simple Directory

Simply mirroring two directories on a single server is one of the easiest ways to use the mirror command. For verbose logging and output, we’ll use two parameters: the Robocopy /mir command and the /v command. The verbose command lets us see what Robocopy is doing and double-check that the files we wish to copy are being copied.

robocopy D:ArticlesSourceDirectory D:ArticlesDestinationDirectory /mir /v D:ArticlesSourceDirectory D:ArticlesDestinationDirectory

Files from a source directory are mirrored into a destination directory.Files from a source directory are mirrored into a destination directory.

Depending on your requirements, this might be sufficient. The file characteristics are duplicated along with the files, but not the file security settings. The next example you may want to look at is how to copy files effectively while keeping the security intact.

Permissions for Mirroring a Directory

The /sec and /secfix commands are used to do a similar mirror operation while correctly copying file and folder permissions. For altered files, the /sec command copies the file security across, whereas the /secfix command updates the security for unchanged files. You may successfully mirror all of the files, directories, and permissions from a source directory to a destination by combining these commands with /mir.

We have a directory with four files in this example, same as we did in the previous. In addition, the permissions on test2.txt have been changed to add an extra user with modify permissions.

security aspects of test2.txtsecurity aspects of test2.txt

We’ll also change the permissions on test3.txt in the destination folder to show how the /sec and /secfix options work to ensure that permissions are correctly copied over.

security characteristics of test3.txtsecurity characteristics of test3.txt

We can see that the user’s permissions have been transferred across after performing the following command. The right permissions were replicated but the file contents remained synchronized since the files were identical but had different permissions.

If you receive an access forbidden message while moving files across, make sure to run as administrator. Depending on the security settings of your system, establishing permissions may need administrator access.

robocopy /mir /sec /secfix /v D:ArticlesSourceDirectory D:ArticlesDestinationDirectory

Files from a source directory are mirrored into a destination directory. copying security settings as wellFiles from a source directory are mirrored into a destination directory. copying security settings as well

We can see that the test2.txt file, which had its source permissions altered, transferred to the destination folder with the proper rights.

security aspects of test2.txtsecurity aspects of test2.txt

If we look at test3.txt, which had its destination directory permissions modified, we can see that the file has now restored to its original source directory rights.

security characteristics of test3.txtsecurity characteristics of test3.txt

Over the Network: Using the Mirror Command

This command works as well over the network, but there are a few other commands that may be used in combination with the /mir command to improve speed and performance.

  • /zb – Use restartable mode, and if access is denied, switch to backup mode (shadow mode)
  • /MT:nn — Copy files with multiple threads, which you specify by substituting the nn placeholder with the desired number of threads. The default is 8, and 16 is a good amount to start with. Keep in mind that running more threads will need more CPU and memory.
  • – /tbd – /tbd – /tbd If you’re moving files over network shares, you can get Error 67, which means “network name cannot be identified,” and this option will try again.
  • /r:1 /w:3 – These two instructions tell Robocopy to only retry once and to wait three seconds between retries. This amount should be modified as needed, for example, 5-10 retries with 5 seconds between them; otherwise, it will retry endlessly with 30 seconds between them.
  • /fft – Finally, the FFT option utilizes FAT file time rather than NTFS file timing, which may result in a 2-second drift and less precision but greater robustness while moving data. This is also necessary when moving files between NTFS and EFS file systems.
  • /np — Removes the progress bar indication, which may become erroneous due to the transfer’s multi-threaded nature.

Because the /z command may sometimes cause performance to slow down, you may need to test with and without it to get the best performance and dependability.

You’ll have a reliable solution for mirroring files across the network if you use all of these instructions together. We’re mirroring files from a local directory to a remote file share using the remote server’s fully qualified domain name (FQDN) to illustrate this functionality.

You should have a strong yet performant solution to delivering files over the network if you use restartable backup mode, multi-threading, share error handling, FAT file timing, and optimized retry and wait times.

robocopy D:ArticlesSourceDirectory /mir /zb /mt:16 /tbd /r:1 /w:3 /fft /np server1.fqdnDestinationShare

You’ll note that we didn’t use the /sec or /secfix commands in this case. The cause for this is determined by your surroundings. If you’re transferring files across domain shares, all rights should transfer correctly, unless they’re unique local permissions.

If you’re moving files across operating systems, domain shares, or non-domain connected PCs, skipping these procedures may be the best option.

Adjust the multi-threading as needed to get the best possible balance of system performance, bandwidth, and transfer rates.


Complex file transmission requirements are common among system administrators. Despite the introduction of a slew of new tools and solutions, Robocopy /mir remains a popular option. Robocopy, which is included with Windows and is updated on a regular basis to keep up with new Windows versions, is still a useful utility for moving data.

Robocopy is a strong tool, and the Robocopy /mir command, in particular, provides for reliable and practical file and folder mirroring across folders and network shares. Robocopy becomes even more powerful and dependable when using the Robocopy /mir command to copy files over a network with the inclusion of a few handy commands.

The “robocopy commands” is a command-line tool that allows users to copy files and folders between two locations. The “MIR Switch” is a feature of the Robocopy command-line tool that allows users to switch the source and destination folder during file copying.

Frequently Asked Questions

How do you speed up Robocopy?

A: Unfortunately, Robocopy does not have a feature to speed up the copying process. If you want to increase its speed, we recommend that you use the following command line parameters in Windows PowerShell:
-verbose – compression level=fast 。

Does Robocopy Mir copy permissions?

A: Robocopy doesn’t have any permissions to copy or move files.

What is better than Robocopy?

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