• NTFS File System Setting
  • Networking Subsystem Performance Settings for IIS
  • Server Message Block Model
  • SMB Configuration Considerations
  • Tuning Parameters for SMB File Servers
  • SMB Server Tuning Example
  • Other Issues that Affect IIS Performance

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    Other Issues that Affect IIS Performance

    The following issues affect IIS performance:

    Installation of filters that are not cache-aware.

    The installation of a filter that is not HTTP-cache-aware causes IIS to completely disable caching, which results in poor performance. Old ISAPI filters that were written before IIS 6.0 can cause this behavior.

    Common Gateway Interface (CGI) requests.

    For performance reasons, the use of CGI applications for serving requests is not recommended under IIS. The frequent creation and deletion of CGI processes involves significant overhead. Better alternatives include the use of ISAPI application and ASP or ASP.NET scripts. Isolation is available for each of these options.

    NTFS File System Setting

    Under HKLM\System\CurrentControlSet\Control\FileSystem\ is NtfsDisableLastAccessUpdate (REG_DWORD) 1.

    This system-global switch reduces disk I/O load and latencies by disabling the updating of the date and time stamp for the last file or directory access. This key is set to 1 by default. Clean installations of Windows Server 2008 and Windows Server 2008 R2 set this key by default and you do not need to adjust it. Earlier versions of Windows operating systems did not set this key. If your server is running an earlier version of Windows or was upgraded to Windows Server 2008 or Windows Server 2008 R2, you should set this key to 1.

    Disabling the updates is effective when you are using large data sets (or many hosts) that contain thousands of directories. We recommend that you use IIS logging instead if you maintain this information only for Web administration.

    Caution: Some applications such as incremental backup utilities rely on this update information and do not function correctly without it.

    Networking Subsystem Performance Settings for IIS

    See “Performance Tuning for Networking Subsystem” earlier in this guide.

    Performance Tuning for File Servers

    Selecting the Proper Hardware for Performance

    You should select the proper hardware to satisfy the expected file server load, considering average load, peak load, capacity, growth plans, and response times. Hardware bottlenecks limit the effectiveness of software tuning. “Choosing and Tuning Server Hardware” earlier in this guide provides recommendations for hardware. The sections on networking and storage subsystems also apply to file servers.

    Server Message Block Model

    This following sections provide information about the Server Message Block (SMB) model for client-server communication, including the SMB 1 and SMB 2 protocols.

    SMB Model Overview

    The SMB model consists of two entities: the client and the server.

    On the client, applications perform system calls by requesting operations on remote files. These requests are handled by the redirector subsystem (Rdbss.sys) and the SMB mini-redirector (Mrxsmb.sys), which translate them into SMB protocol sessions and requests over TCP/IP. Starting with Windows Vista, the SMB 2 protocol is supported. The Mrxsmb10.sys driver handles legacy SMB traffic, and the Mrxsmb20.sys driver handles SMB 2 traffic.

    On the server, SMB connections are accepted and SMB requests are processed as local file system operations through NTFS and the local storage stack. The Srv.sys driver handles legacy SMB traffic, and the Srv2.sys driver handles SMB 2 traffic. The Srvnet.sys component implements the interface between networking and the file server for both SMB protocols. File system metadata and content can be cached in memory through the system cache in the kernel (Ntoskrnl.exe).

    Figure 6 summarizes the different layers that a user request on a client machine must pass through to perform file operations over the network on a remote SMB file server that uses SMB 2.

    Windows 7 and Windows Server 2008 R2 introduce SMB 2.1. The new protocol version has optimizations to reduce network chattiness, which improves overall performance.
    Figure 6. Windows SMB Communication Model Components

    SMB Configuration Considerations

    Do not enable any services or features that your particular file server and file clients do not require. These might include SMB signing, client-side caching, file system minifilters, search service, scheduled tasks, NTFS encryption, NTFS compression, IPSEC, firewall filters, Teredo, and antivirus features.

    Ensure that any BIOS and operating system power management mode is set as needed, which might include High Performance mode. Ensure that the latest and fastest storage and networking device drivers are installed.

    Copying files is one of the common operations performed on a file server. Windows has several built-in file copy utilities that you can run in a command shell, including xcopy and robocopy. When you use xcopy, we recommend adding the /q and /k options to your existing parameters, when applicable, to maximize performance. The former option reduces CPU overhead by reducing console output and the latter reduces network traffic. When using robocopy, the /mt option (new to Windows Server 2008 R2) can significantly improve speed on remote file transfers by using multiple threads when copying multiple small files. We also recommend the /log option to reduce console output by redirecting to NUL or to a file.

    Previous releases of Windows Server sometimes benefitted from tools that limit the working-set size of the Windows file cache. These tools are not necessary on most servers running Windows Server 2008 R2. You should reevaluate your use of such tools.

    Tuning Parameters for SMB File Servers

    The following registry tuning parameters can affect the performance of SMB file servers:


    The default is 0. This parameter determines whether NTFS generates a short name in the 8.3 (MSDOS®) naming convention for long file names and for file names that contain characters from the extended character set. If the value of this entry is 0, files can have two names: the name that the user specifies and the short name that NTFS generates. If the user-specified name follows the 8.3 naming convention, NTFS does not generate a short name.

    Changing this value does not change the contents of a file, but it avoids the short-name attribute creation for the file, which also changes how NTFS displays and manages the file. For most SMB file servers, the recommended setting is 1.

    Starting with Windows Server 2008 R2, you can disable 8.3 name creation on a per-volume basis without using the global NtfsDisable8dot3NameCreation setting. You can do this with the built-in fsutil tool. For example, to disable 8.3 name creation on the d: volume, run fsutil 8dot3name set d: 1 from a command prompt window. You can view help text by using the command fsutil 8dot3name.

    • TreatHostAsStableStorage

    The default is 0. This parameter disables the processing of write flush commands from clients. If the value of this entry is 1, the server performance and client latency for power-protected servers can improve. Workloads that resemble the NetBench file server benchmark benefit from this behavior.

    • AsynchronousCredits



    The default is 512. This parameter limits the number of concurrent asynchronous SMB commands that are allowed on a single connection. Some file clients such as IIS servers require a large amount of concurrency, with file change notification requests in particular. The value of this entry can be increased to support these clients.

    • Smb2CreditsMin and Smb2CreditsMax



    The defaults are 64 and 1024, respectively. These parameters allow the server to throttle client operation concurrency dynamically within the specified boundaries. Some clients might achieve increased throughput with higher concurrency limits. One example is file copy over high-bandwidth, high-latency links.

    • AdditionalCriticalWorkerThreads

    HKLM\System\CurrentControlSet\Control\Session Manager\Executive\(REG_DWORD)
    The default is 0, which means that no additional critical kernel worker threads are added to the default number. This value affects the number of threads that the file system cache uses for read-ahead and write-behind requests. Raising this value can allow for more queued I/O in the storage subsystem and can improve I/O performance, particularly on systems with many processors and powerful storage hardware.

    • MaximumTunnelEntries

    The default is 1024. Reduce this value to reduce the size of the NTFS tunnel cache. This can significantly improve file deletion performance for directories that contain a large number of files. Note that some applications depend on NTFS tunnel caching.

    • MaxThreadsPerQueue



    The default is 20. Increasing this value raises the number of threads that the file server can use to service concurrent requests. When a large number of active connections need to be serviced and hardware resources (such as storage bandwidth) are sufficient, increasing the value can improve server scalability, performance, and response times.



    The default is 0. Changing this value to 1 prevents SMB communication with machines where SMB signing is disabled. In addition, a value of 1 causes SMB signing to be used for all SMB communication. SMB signing can increase CPU cost and network round trips. If SMB signing is not required, ensure that the registry value is 0 on all clients and servers.

    MaxMpxCt (not applicable with SMB 2 clients)


    The default is 50. This parameter suggests a limit on the maximum number of outstanding requests that an SMB 1 client can send. Increasing the value can use more memory, but can improve performance for some client applications by enabling deeper request pipelining. Increasing the value in conjunction with MaxCmds can also eliminate errors encountered due to large numbers of outstanding long-term file requests, such as FindFirstChangeNotification calls. This parameter does not affect connections with SMB 2 clients.



    The default is 1. In versions of Windows prior to Windows Vista and Windows Server 2008, the default is 0 (do not disable last access). A value of 0 can reduce performance because the system performs additional storage I/O when files and directories are accessed to update date and time information.

    The following parameters are no longer required:










    SMB Server Tuning Example

    The following settings can optimize a machine for file server performance in many cases. The settings are not optimal or appropriate on all machines. You should evaluate the impact of individual settings before applying them.















    MaxMpxCt (not applicable with SMB 2 clients)


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    Other Issues that Affect IIS Performance

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