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Troubleshooting slow SMB transfer

asked 2019-05-16 23:27:21 +0000

neteng.ams gravatar image

I have a Windows machine transferring files with a NetApp through a firewall on the local LAN (1 gbit), but getting very slow transfers. In this PCAP, only 150 MB in transferred after 20 seconds. How do I troubleshoot this?

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answered 2019-05-17 08:43:20 +0000

SteveZhou gravatar image

updated 2019-05-17 08:44:37 +0000

So it is the client was writing to the server. Several things:

  1. The client seems to have the TSO feature enabled on the NIC so we cannot see each of the MSS-size tcp segment but a single large segment from smb which have us pain on sequence analysis.

  2. window full was observed from the NetApp server, which indicates that the server-side process power cannot keep in pace with the incoming packets.

  3. looks like delayed-Ack was disabled.

  4. would like to see the performance while the client was in the same subnet as the NetApp gear, just to quickly isolate the issue out of any intermediate devices.

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Asked: 2019-05-16 23:27:21 +0000

Seen: 1,180 times

Last updated: May 17 '19