Performance Drops During Large File Copy

• Microsoft Windows NT operating system version 3.1
• Microsoft Windows NT Advanced Server version 3.1
• Microsoft Windows NT Server versions 3.5, 3.51, and 4.0

SYMPTOMS

System performance drops to an unacceptable level while a large file is being copied.

CAUSE

This problem may be a symptom of a problem with the way that the Server service interacts with the system cache in certain configurations.

RESOLUTION

You may be able to work around this problem by tuning the server to prevent the providing of large amount of memory to the system cache.

To do this, perform the following steps:

1. Start Control Panel Network.

2. From the Installed Network Software box, select Server, and then click Configure.

3. If the option "Maximize Throughput for File Sharing" is currently selected, you may get better performance during large file copy operations by selecting the "Maximize Throughput for Network Applications" or "Balance" options.

4. If you elected to make a change in Step 3, restart your computer so the change can take effect.

MORE INFORMATION

The "Maximize Throughput for File Sharing" option permits the system cache to use more available memory than it would otherwise. In this situation, the available memory can drop to levels that result in heavy swapping activity on the hard disks in order to accommodate requests from user or system applications that may subsequently need to be swapped into memory.

The cache manager periodically gives up memory that it has allocated so that the system will never run completely out of memory due to caching alone. This can happen whenever a file copy operation is complete or when a threshold value is reached. This means that the problem described above does not occur if a series of smaller files are copied. The threshold value, when "Maximize Throughput for File Sharing" option is not selected, is enough higher than the threshold value when the problem does not occur there either.

This problem is also more noticeable on computers with lower total physical memory. When more total physical memory is available, the minimum available memory threshold is also higher, which can alleviate the problem.

The article referenced below explains the registry setting LargeSystemCache, the setting which is changed when changes are made to the Maximize Throughput server service settings. For Additional information, please see the following article in the Microsoft Knowledge Base:

         Article ID:  Q101041
         Title     : Excessive and Unnecessary Paging Activity

STATUS

Microsoft has confirmed this to be a problem in Windows NT and Windows NT Advanced Server version 3.1. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.