DOCUMENT:Q110255  20-JAN-1994  [W_NT]
TITLE   :Performance Drops During Large File Copy
PRODUCT :Windows NT
PROD/VER:3.10
OPER/SYS:WINDOWS
KEYWORDS:

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The information in this article applies to:

 - Microsoft Windows NT operating system version 3.1
 - Microsoft Windows NT Advanced Server version 3.1
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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 balance
memory use. To do this, do the following steps:

1. In the Control Panel window, choose the Network icon.

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

3. If either of the options "Maximize Throughput for File Sharing" or
   "Maximize Throughput for Network Applications" are currently selected,
   you may get better performance during large file copy operations by
   selecting the Balance option. If Balance or Minimize Memory Used is
   already selected, this article does not apply.

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

MORE INFORMATION
================

The two options that are designed to maximize network throughput each
permit 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
for the Balance option is enough higher than the threshold values for the
options designed to maximize throughput that 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.

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.

Additional reference words: 3.10
KBCategory:
KBSubCategory: netsrv


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Copyright Microsoft Corporation 1994.