When doing a file level migration, care must be taken to copy the data from the source to destination. A common mistake is the tool used to copy the data. A standard Windows copy to move data, while very simple to execute will strip out much of the metadata and in some cases the metadata is just a crucial to the files as the data themselves. To solve this problem, one tool that can be used is robocopy.
First, let’s show what happens with a windows copy when trying to migrate a few files.
I created a folder with a Word Doc and a change to the NTFS permissions of the file.
The user account “NoAccess” has a full Deny access on this file. We will then go ahead and move the file with the Windows Copy tool.
We will then look at the target folder and we do see the file as expected. The contents of the file are the same. However, when we look at the file security properties on the target side, we see the following.
The security information of the file is missing. This is because the contents of the file are lost when you use a Windows Copy. The user doing the copying becomes the owner and it inherits the security information from that user. If there are any special permissions, groups, or other security metadata on the file, they are lost in a Windows Copy migration.
In comes robocopy. Here, we can copy the file over to the target with the security info intact. Here, I will recopy the data, but this time with a couple of switches to retain the metadata.
Here, we can see that I copied over the Word file. Checking on the security info of the file, we see that the security info of the file did indeed copy over with the file.
This is because robocopy has the ability to copy over the metadata of the files it copies.
The basic syntax for robocopy is simple.
Robocopy <source folder> <target folder> [files to copy default is *.*] [switches]
The first two options are the source and target folders. Then you can specific files if you wish to only copy a subset of the data in the files.
The switches that I used for a simple, one time copy are as follows.
/Z makes this job restartable. If the job fails part way though, such as a network error, ctrl-C, I will be able to pick up where I left off without recopying all of the data over again. For a simple 1 file test such as this, it may seem silly, but if you are copying millions of files to move a large file system from one system to another, having the ability to restart after an unplanned failure is a great peace of mind.
/E Will copy the subdirectories in the source to the target. This will include empty subdirectories.
/SEC will copy the files’ security information to the target files.
/R:3 and /W:1 is for the number of retries on files that the command can not copy, and how long to wait between retries. Although optional, the default values is to wait 30 seconds between retries and will retry a whopping 1 million times! If you are copying live data that is being accessed by the user community, you will probably encounter a few files that you will not be able to copy due to it being opened by other user. Obviously, we do not want to wait a ridiculous amount of time for the file to fail out when we can just skip it over and pick it up on the next run.
Robocopy has a great numbers of options to help with your file based migrations. Although this is just scratching the surface, these options you will find to be used in a majority of your robocopy commands in your migration efforts..