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Performance tuning for file servers

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.

General tuning parameters for clients

The following REG_DWORD registry settings can affect the performance of client computers that interact with SMB file servers:

  • ConnectionCountPerNetworkInterface

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\ConnectionCountPerNetworkInterface

    Applies to Windows 10, Windows 8.1, Windows 8, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, and Windows Server 2012

    The default is 1, and we strongly recommend using the default. The valid range is 1-16. The maximum number of connections per interface to be established with a server for non-RSS interfaces.

  • ConnectionCountPerRssNetworkInterface

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\ConnectionCountPerRssNetworkInterface

    Applies to Windows 10, Windows 8.1, Windows 8, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, and Windows Server 2012

    The default is 4, and we strongly recommend using the default. The valid range is 1-16. The maximum number of connections per interface to be established with a server for RSS interfaces.

  • ConnectionCountPerRdmaNetworkInterface

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\ConnectionCountPerRdmaNetworkInterface

    Applies to Windows 10, Windows 8.1, Windows 8, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, and Windows Server 2012

    The default is 2, and we strongly recommend using the default. The valid range is 1-16. The maximum number of connections per interface to be established with a server for RDMA interfaces.

  • MaximumConnectionCountPerServer

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\MaximumConnectionCountPerServer

    Applies to Windows 10, Windows 8.1, Windows 8, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, and Windows Server 2012

    The default is 32, with a valid range from 1-64. The maximum number of connections to be established with a single server running Windows Server 2012 across all interfaces.

  • DormantDirectoryTimeout

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\DormantDirectoryTimeout

    Applies to Windows 10, Windows 8.1, Windows 8, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, and Windows Server 2012

    The default is 600 seconds. The maximum time server directory handles held open with directory leases.

  • FileInfoCacheLifetime

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\FileInfoCacheLifetime

    Applies to Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008

    The default is 10 seconds. The file information cache timeout period.

  • DirectoryCacheLifetime

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\DirectoryCacheLifetime

    Applies to Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008

    The default is 10 seconds. This is the directory cache timeout.

    Note

    This parameter controls caching of directory metadata in the absence of directory leases.

    Note

    A known issue in Windows 10, version 1803, affects the ability of Windows 10 to cache large directories. After you upgrade a computer to Windows 10, version 1803, you access a network share that contains thousands of files and folders, and you open a document that is located on that share. During both of these operations, you experience significant delays.

    To resolve this issue, install Windows 10, version 1809 or a later version.

    To work around this issue, set DirectoryCacheLifetime to 0.

    This issue affects the following editions of Windows 10:

    • Windows 10 Enterprise, version 1803
    • Windows 10 Pro for Workstations, version 1803
    • Windows 10 Pro Education, version 1803
    • Windows 10 Professional, version 1803
    • Windows 10 Education, version 1803
    • Windows 10 Home, version 1803

  • DirectoryCacheEntrySizeMax

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\DirectoryCacheEntrySizeMax

    Applies to Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008

    The default is 64 KB. This is the maximum size of directory cache entries.

  • FileNotFoundCacheLifetime

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\FileNotFoundCacheLifetime

    Applies to Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008

    The default is 5 seconds. The file not found cache timeout period.

  • CacheFileTimeout

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\CacheFileTimeout

    Applies to Windows 8.1, Windows 8, Windows Server 2012, Windows Server 2012 R2, and Windows 7

    The default is 10 seconds. This setting controls the length of time (in seconds) that the redirector will hold on to cached data for a file after the last handle to the file is closed by an application.

  • DisableBandwidthThrottling

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\DisableBandwidthThrottling

    Applies to Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008

    The default is 0. By default, the SMB redirector throttles throughput across high-latency network connections, in some cases to avoid network-related timeouts. Setting this registry value to 1 disables this throttling, enabling higher file transfer throughput over high-latency network connections.

  • DisableLargeMtu

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\DisableLargeMtu

    Applies to Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008

    The default is 0 for Windows 8 only. In Windows 8, the SMB redirector transfers payloads as large as 1 MB per request, which can improve file transfer speed. Setting this registry value to 1 limits the request size to 64 KB. You should evaluate the impact of this setting before applying it.

  • RequireSecuritySignature

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\RequireSecuritySignature

    Applies to Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008

    The default is 0, disabling SMB Signing. Changing this value to 1 enables SMB signing for all SMB communication, preventing SMB communication with computers where SMB signing is disabled. SMB signing can increase CPU cost and network round trips, but helps block man-in-the-middle attacks. If SMB signing is not required, ensure that this registry value is 0 on all clients and servers.

    For more info, see The Basics of SMB Signing.

  • FileInfoCacheEntriesMax

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\FileInfoCacheEntriesMax

    Applies to Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008

    The default is 64, with a valid range of 1 to 65536. This value is used to determine the amount of file metadata that can be cached by the client. Increasing the value can reduce network traffic and increase performance when a large number of files are accessed.

  • DirectoryCacheEntriesMax

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\DirectoryCacheEntriesMax

    Applies to Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008

    The default is 16, with a valid range of 1 to 4096. This value is used to determine the amount of directory information that can be cached by the client. Increasing the value can reduce network traffic and increase performance when large directories are accessed.

  • FileNotFoundCacheEntriesMax

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\FileNotFoundCacheEntriesMax

    Applies to Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008

    The default is 128, with a valid range of 1 to 65536. This value is used to determine the amount of file name information that can be cached by the client. Increasing the value can reduce network traffic and increase performance when a large number of file names are accessed.

  • MaxCmds

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\MaxCmds

    Applies to Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008

    The default is 15. This parameter limits the number of outstanding requests on a session. Increasing the value can use more memory, but it can improve performance by enabling a deeper request pipeline. Increasing the value in conjunction with MaxMpxCt can also eliminate errors that are encountered due to large numbers of outstanding long-term file requests, such as FindFirstChangeNotification calls. This parameter does not affect connections with SMB 2.0 servers.

  • DormantFileLimit

    HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\DormantFileLimit

    Applies to Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista, Windows Server 2022, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008

    The default is 1023. This parameter specifies the maximum number of files that should be left open on a shared resource after the application has closed the file.

Client tuning example

The general tuning parameters for client computers can optimize a computer for accessing remote file shares, particularly over some high-latency networks (such as branch offices, cross-datacenter communication, home offices, and mobile broadband). The settings are not optimal or appropriate on all computers. You should evaluate the impact of individual settings before applying them.

Parameter Value Default
DisableBandwidthThrottling 1 0
FileInfoCacheEntriesMax 32768 64
DirectoryCacheEntriesMax 4096 16
FileNotFoundCacheEntriesMax 32768 128
MaxCmds 32768 15

Starting in Windows 8, you can configure many of these SMB settings by using the Set-SmbClientConfiguration and Set-SmbServerConfiguration Windows PowerShell cmdlets. Registry-only settings can be configured by using Windows PowerShell as well.

Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters" RequireSecuritySignature -Value 0 -Force