Sql-server – SQL Server Bulk insert over UNC path failing, despite full access

It looks like the ReportServer virtual directory is being processed by SharePoint still. You need to set it up as an exclusion in SharePoint. To do this, switch to the SharePoint 12 hive (C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\bin) and run the command:

stsadm -o addpath -url http://<sharepointurl>/<ReportServer vdir> -type exclusion
stsadm -o addpath -url http://<sharepointurl>/<Reports vdir> -type exclusion

Unfortunately, the behaviour you witnessed is by design:

http://msdn.microsoft.com/en-us/library/ms188365.aspx [Security Account Delegation (Impersonation)] http://msdn.microsoft.com/en-us/library/ms175915.aspx [Security Considerations] http://msdn.microsoft.com/en-us/library/ms161965.aspx

From the second link:

The way in which SQL Server 2005 and later versions control access to files addresses a security issue that was present in Microsoft SQL Server 2000 and earlier versions. Formerly, after a user was authenticated, access to external files was based on the security profile of the SQL Server process. When the SQL Server process had read access to a file, for a user that did not have access to the file but was a member of the bulkadmin fixed server role, the user could import the file by using BULK INSERT and access the contents of the file.

Your only options are either using a SQL Server login or giving SQL Server the needed rights to perform delegation.

A possible solution could be to run a job to copy the file from ServerA to ServerB (I assume your service account has write access to both of them), and then have SQL Server on ServerB perform the import from its local disk.