Trouble Downloading large SharePoint files over Mapped Drives

I recently ran into a problem where I have a SharePoint customer trying and downloading large files from mapped drive going to their shared documents.  I could download the file directly from their site using a browser but I couldn’t download the same file from the mapped drive location. The file in question was 1.2GB in size.

When trying to move/copy the file it would site for while on ‘calculating’ but in the end it would return:
Cannot Copy FileName: Cannot read from the source file or disk’

After some digging I was able to find out it was client side issue related to how Windows clients treat WebDav connection. In essence mapped drives to a SharePoint Share Document library is a WeDav connection. Any files greater than 50000000 bytes or approximatly 50MB are not allowed because the behavior is interpreted as attack.

To fix the issues you have to make the following registry change.

To resolve this issue, follow these steps:

  1. Click Start, click Run, type regedit, and then click OK.
  2. Locate and then click the following registry subkey:
  3. In the right pane, right-click the FileSizeLimitInBytes value, and then click Modify.
    If you cannot see the FileSizeLimitInBytes value, right-click the blank space in the right pane, click New, click DWORD Value, type FileSizeLimitInBytes, and then click OK.
  4. In the Edit DWORD Value box, click to select the Decimal option. In the box under Value data, type a value that is larger than the size of the file that you want to download. Click OK.
    Note: The default value for the file size limit is 50000000 bytes.
  5. Quit Registry Editor. Restart the computer.

You will want to make sure you are saving your registry backup in case you run into any problems.


Source: Microsoft KB

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