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What is the default, minimum, maximum, and recommended value for cifs.tcp_window_size in Data ONTAP 7-Mode?

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Applies to

  • Data ONTAP 8 7-Mode
  • Data ONTAP 8.1 7-Mode
  • Data ONTAP 8.2 7-Mode

Answer

Adjusting the CIFS TCP window size might be required while performing performance tuning, since the TCP window size controls the number of TCP messages that can be transmitted between the storage system and the CIFS client at one time. This article describes how to decide the optimal TCP window size and what are the limitations for the TCP window size, both on the storage system end and on the Windows clients.

  • How to view/modify the CIFS TCP window size on the storage system end?
    Run the following command to view/modify the CIFS TCP window size on the storage system operating in Data ONTAP 7-Mode:
    Filer> options cifs.tcp_window_size
    • This bedome effective with a restart of CIFS or when a new name is registered as a NetBIOS alias. If you are not restarting CIFS, only the newly registered names will have the changed window size. When registering a NetBIOS alias, CIFS looks at the controller's registry key options.cifsinternal.aliaswindowsize to get the value to use. This value is updated whenever a NetBIOS alias is created and it uses the then-current value of cifs.tcp_window_size. This registry value is maintained separately from the current value of cifs.tcp_window_size
  • What are the limitations of cifs.tcp_window_size?
    Default value = 17520 bytes
    Minimum value = 1600 bytes
    Maximum value = 8388608 bytes(8M)

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