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What is the impact of modifying the nfs server option '-tcp-max-xfer-size'?

  1. Last updated
    Apr 25, 2025
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Category:
ontap-9
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nas
Last Updated:
4/25/2025, 12:43:51 PM

Applies to

  • ONTAP 9
  • NFS

Answer

  • There is no impact to new mount(s), will receive the max operation size of tcp-max-xfer-size
  • Existing mounts are not impacted until the client requests for this information again (normally only done on mount
  • Larger transfer sizes reduce the number of communications, which is expected to mitigate the impact of RTT.
  • It is anticipated that the number of RPC calls will be reduced, leading to a decrease in CPU load.
  • It is expected to work favorably for large files.
  • If any part of the network does not support large transfer sizes, fragmentation may occur, which can lead to increased latency.
  • In the event of a transfer error, retransmission of larger sizes may be required, resulting in an increased volume of unnecessary transmissions that negatively impact network bandwidth.
  • Performing large transfers consumes more memory or buffers.

Additional Information

ONTAP NFS transfer sizes

WARNING

  • Due to the behavior of various operating systems, NetApp does not suggest to decrease the maximum allowable transfer size on ONTAP below the value of rsize/wsize of currently mounted NFS file systems
  • This can create hangs or even data corruption with some operating systems

 

 

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