This help article explains the setup required for proper file uploads in a Web Farm when load balancing is used.
There are a few simple requirements that allow file uploads (including chunk file uploads) to arrive in the proper destination:
TargetFoldermust be in a location shared among all servers. For example,
You can create a Virtual Directory under the WebApplication and point it to the shared network location. You can then use this virtual directory for the RadAsyncUpload
The Windows user account that the ApplicationPool uses must have permissions to read and write to these folders. Setting the
trueinstructs the control to impersonate the application pool.
Depending on your host, you may find useful the built-in support RadCloudUpload offers for:
If files do not get written at all to the target folder, try giving
Everyone permissions to the
TemporaryFolder. If this resolves the issue, then you need to locate the user that IIS operates under, and provide them with sufficient privileges. Set the
UseApplicationPoolImpersonation property of the RadAsyncUpload to
Such a shared drive can be considered a single point of failure, which is something load balancing and web farms strive to avoid. If this is a concern in your use case, set
true so that the files will be uploaded in one piece and use a custom upload handler to store them according to your application requirements.
Large files must be allowed by the server. For more details, see the Uploading large files article.