iRODS WebDAV access by Windows for > 4GB files / objects

[Blake Fitch]

Hello All,

We export iRODS data using the WebDAV interface. This works for Linux, Mac, and Windows. Our user base is largely on Win10. We can mount iRODS as a file system using the native Win10 capabilities. However, we find that we cannot access files/objects that are larger than 4GB. (This works fine from Linux -- so the server side probably isn't the problem.)

The question we have is: How do organizations with a Windows based user base provide access to large (order 100GB)  iRODS files/objects via the file system?

Here are some links discussing this problem.

"This sets the maximum you can download from the WebDAV to 4 GB at one time, where 4 GB is the maximum value supported by Windows OS."

From:
https://docs.druva.com/Knowledge_Base/inSync/Troubleshooting/WebDAV_download_fails_with_file_size_exceeds__the_limit_error

Also see:
https://support.microsoft.com/en-us/topic/folder-copy-error-message-when-downloading-a-file-that-is-larger-than-50000000-bytes-from-a-web-folder-815e2949-0f56-ec25-db7d-b6d860a31f77

Any thoughts or suggestions would be most appreciated.

Best,
Blake

[Smeele, A.P.M. (Ton)]

The built-in WebDAV redirector driver in Windows uses a DWORD configuration parameter that specifies a maximum file size. Files that exceed this size cannot be accessed.

Microsoft claim they have designed this limitation as a security feature, avoiding DenialOfService attacks by limiting access (see: "cause" inhttps://support.microsoft.com/en-us/topic/folder-copy-error-message-when-downloading-a-file-that-is-larger-than-50000000-bytes-from-a-web-folder-815e2949-0f56-ec25-db7d-b6d860a31f77).

As it is not possible to express a value larger than 4 GBytes in a DWORD in the configuration parameter, this effectively limits your options for allowing access to larger files through a Windows WebDAV mount. Unfortunately they forgot to include an "unlimited" option.

A workaround is to licence and install an alternative (non)commercial driver. Some examples are MountainDuck and NetDrive, there are many more.

Ton

--