DOCUMENT:Q119870 07-FEB-2002 [winnt] TITLE :Redirector Uses Core Mode on Large File Transfers PRODUCT :Microsoft Windows NT PROD/VER::3.5 OPER/SYS: KEYWORDS: ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Workstation version 3.5 - Microsoft Windows NT Server version 3.5 ------------------------------------------------------------------------------- SYMPTOMS ======== When you copy a large file to or from a Windows NT Workstation and Windows NT Server version 3.5 computer, the redirector may switch to core mode during the transfer. The use of core mode increases the time required to transfer the file. The switch to core mode occurs after approximately 20 megabytes (MB) have been transferred and is more likely to occur when transferring a file to a Windows NT server, but it can occur in either direction. Core mode over FDDI requires more bandwidth than over Ethernet or token ring, so the symptoms are more pronounced on fiber. Smaller files transfer in raw mode. CAUSE ===== Raw I/O requires exclusive access to the virtual circuit, meaning the virtual circuit must be effectively "locked" for the duration of the raw I/O. If other activity is occurring on the circuit at the time the redirector tries to do raw I/O, the circuit cannot be "locked" so the redirector uses core I/O instead. One reason the virtual circuit cannot be "locked" is that as the file data is being written, the file also needs to be extended which also requires network activity. The reason the problem surfaces at a large offset into the file has to do with when the lazy writer and modified page writer start their work. When the system starts running short of free pages, the modified page writer wakes up. Unfortunately, the modified page writer likes to write one page at a time. The redirector cannot turn a 4K write into a raw I/O. The correction to the problem will require changes to both the redirector and the memory manager. RESOLUTION ========== A new redirector is in the works, but will not be ready for at least a year. It will not be corrected in the final release of Windows NT 3.5. STATUS ====== Microsoft has confirmed this to be a problem in Windows NT version 3.5. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available. Additional query words: prodnt 3.50 ====================================================================== Keywords : Technology : kbWinNTsearch kbWinNTWsearch kbWinNT350search kbWinNTW350 kbWinNTW350search kbWinNTSsearch kbWinNTS350 kbWinNTS350search Version : :3.5 ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2002.