The cause of network file copy issues are frequently difficult to determine. This article describes how to troubleshoot network file copy failures and network file copy performance issues.
NOTE: This article assumes that you have the correct credentials to perform the file copy operation, that files and folders are configured with the correct permissions, and that name resolution is functioning correctly on the network.
Troubleshoot Network File Copy Failures
To troubleshoot network file copy failures, perform any of the following procedures, as appropriate to your situation:
Test the File Copy Operation on the Local Segment
Verify that you can copy files locally. If you cannot copy files on the local segment, rule out any issues that may be caused by network devices—such as switches or routers—between the end points. One method of eliminating network devices is to connect both end-point systems to a hub. Otherwise, use a network sniffer (such as Microsoft Network Monitor) to capture network data to determine if packet loss is occurring as a result of a faulty network device.
Windows 2000 Server Remote Access Connections
If you connect to the network by using the remote access service, try to copy files between your computer (the remote access client) and the remote access server before you try to copy files to other computers on the remote network. If you can copy files between your computer and the server but you cannot copy files between your computer and another computer on the remote network, verify whether file copy operations are successful between the remote access server and the remote computer.
Compress the file, and then test to see whether you can perform the network file copy operation. By doing so, you can determine the following:
File Locking Issues
When you compress a file, you rule out the issue that the file is locked by another program that is installed on the computer.
Wide Area Network (WAN) Link Issues
If you can copy the file locally but you cannot copy the file across the network, verify whether the link itself is the cause of the packet loss. Some links, such as T1 and Fractional T1, can drop packets based on bit patterns in the data. This can be caused by either a misconfiguration of the Channel Service Unit/Data Service Unit (CSU/DSU) devices at either end of the link or by some interference in the equipment or media that is used in the link.
If you suspect that a faulty link is the cause of the failure, try to copy a file that is not compressed, and then verify that the issue only occurs if the file is in an uncompressed state. Then compress the file, and then try to copy it. Changing the compression state of the file changes the bit pattern of the data in the file and, as a result, can resolve the file copy issue.
For additional information about connection problems across T1 WAN links, click the following article number to view the article in the Microsoft Knowledge Base:
To troubleshoot network file copy performance issues, use any of the following procedures, as appropriate to your situation:
A possible cause of slow file copy performance between Microsoft Windows 2000 and Windows NT 4.0-based computers involves the Nagle algorithm. By default, this algorithm is enabled in Windows NT 4.0 Service Pack 5 (SP5) and earlier. It was first disabled by default in Windows NT 4.0 Service Pack 6a (SP6a) and is also disabled by default in Windows 2000. As a result, a performance issue may occur between computers that run Windows NT 4.0 SP5 or earlier and computers that run Windows NT 4.0 SP6a or later or Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
236316 Performance Improvement for Redirector/Server Connections Involving Small File Operations
Type of Data Copy Method (Raw or Core Mode)
Another possible cause of slow file copy performance may be the type of data transfer that occurs. Data can be copied in either Core mode or Raw mode. Typically, data that is copied by using the command prompt is transferred in Raw mode, and data that is copied by using Windows Explorer is transferred in Core mode. Raw mode results in a faster transfer rate.
The method that you use to copy files affects performance. To determine which mode is used, use a network sniffer, such as Microsoft Network Monitor, to determine which type of transfer occurs.
Slow File Writes from Windows 2000 to Windows NT 4.0 Server
For additional information about how to troubleshoot slow file copy performance when you copy files from a Windows 2000-based computer to a Windows NT 4.0 Server-based computer, click the following article number to view the article in the Microsoft Knowledge Base:
279282 Slow File Write from Windows 2000 to Windows NT 4.0 Server