SMB2 copy issue and SRT
I am having an issue, copying a single large file (2GB) from a Server 2016 to a Windows 10 client. Both client and server on same network and subnet
2 laptops (different models), on one of the laptops copy takes about 5 mins as expected. One another laptop copy takes about 30 mins and in Windwos copy GUi I can see the transfer rate drop to 0 bytes per second and then increase
I took wireshark trace from both laptops and I am suspecting issue with the SMB2.
I did a SMB2 SRT analysis on the 2 laptops and on the laptop with slow copy the READ SRT sum value is very high, compared to the same read on the laptop with the good copy
Am I correct in thinking the issue is related to SMB on the client side
It is propably a combination of factors. But a client which downgrades a connection type will have a dramatic adverse effect on the performance. But without actually looking at the packet capture it is very hard to tell. But in your case I would lok at the details at the start of the session. Nuances in the negotiation may decrease effentiency a lot.
I did further testing can confirm issue is with SMB2
I copied same file from same server to same client using FTP and 2 Gb file took 7 minutes to copy
Same copy using SMB2 takes 30 mins.
I agree, I'd love to see the PCAPs for these transfers so that we could see exactly what is going on.
I would like to say that you have to be careful interpreting Wireshark's SRT values for SMB.
In a long time ago Ask Wireshark question: https://osqa-ask.wireshark.org/questi...
there were very high SRT values - but they weren't a problem with the server at all. They were an artifact of the way that the SMB client made its READ requests. The client issued large bursts of READs all at once, sometimes more than 120 in one go. These were all done within a single TCP connection - meaning that they had to be serviced sequentially.
Imagine 100 READ requests all arrive at the server at once. The 100th will have to spend time in a server queue, waiting for the data in READ-1 through READ-99 to ...(more)