Default Frame Size

Question

I am performing some performance tests on my network, using iPerf (https://iperf.fr/iperf-doc.php#3doc), and wanted to know what is the default buffer size when copying files using SMB (and does it depend which version), for configuring the -w option within iPerf.

Answer 1

Hi ,

For SMBV1, the default buffer size is related with registry value called SizReqBuf. And the default value of SizReqBuf for server SKUs with >= 512MB RAM is 16KB (16,644 bytes). If the server has less than 512MB RAM then the default is 4,356 bytes.

For SMBV2 and SMBV3, default buffer size is 1MB (1024*1024).

Best Regards,
Candy

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Answer 2

The default is 512

Kindly go through the following Microsoft reference:

Performance tuning for SMB file servers

Answer 3

Maybe you can then answer the following question. Assuming I have about 10 SSD drives in a RAID 10 config - I have an enormous amount/capacity of IO and Throughput. My network is 10Gb or faster (each server has at least 10Gb NICs).

Still, nonetheless, when I copy a file from one server to another, I can't usually get a throughput of greater than ~100MB-600MB/sec. I would expect to see performance in the Gb/sec.

Answer 4

Also, another point: These keys you mention here (https://learn.microsoft.com/en-us/windows-server/administration/performance-tuning/role/file-server/) are nice when the source server is a Windows host. But when copying from a Network appliance/storage share, those keys don't help much.

Answer 5

It seems your issue is that slow copy performance between two servers. For slow copy performance, we need to analyze performance log and network traffic to find the cause. However, analysis of log is beyond our forum support level and due to forum security policy, we have no such channel to collect user log information. So, we recommend you open a case with MS Professional tech support service, they will help you open a phone or email case to Microsoft, so that you would get a technical support on a one-to-one basis while ensuring private information.

Here is the link:

https://support.microsoft.com/en-us/gp/customer-service-phone-numbers