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How to set or change the TCP packet window size for Network Data Management Protocol (NDMP) or NDMPcopy.

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ndmp
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dp
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Applies to

7-Mode ONTAP 8.2 and above.
ONTAP 9 and above.

Description

Modifying NDMP tcpwinsize can help increase throughput for indirect / remote or three-way backups and restores over the network. This option controls the NDMP receive buffer and the NDMP send buffer.

  • The default value for all ONTAP versions is 32768 Bytes (32KB).
  • The minimum value is 8192 (8KB). The maximum value is 7MB, the exact value is depending on Data ONTAP version:
    • Data ONTAP 8.2 7-Mode: 7704644
    • Clustered Data ONTAP 8.3: 7631441
    • ONTAP 9 and above: 7285344
  • This option takes effect on the next NDMP operation; existing NDMP sessions are not effected.
  • If you are running an NDMPCopy between separate storage controllers, modify both sides.

The best value for your environment depends on many factors including network latency, available bandwidth, the receive TCP buffer on the secondary storage server, and available controller and secondary storage server resources.

A common method to find the best value is to increase the existing value and re-evaluate throughput. If no improvement is seen, increasing the value further is unlikely to increase throughput.

 

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