As 10Gb CNA’s have become more affordable I continue to see more and more performance related issue where out of the box 10Gb CNA’s may exhibit subpar performance especially during a file copy.
This article specifically applies to a scenario where your CNA regardless of vendor is already performing at or near line speed after initial performance tuning, however your file copy performance is subpar and in many cases you will see large valleys appear during the copy for no obvious reason.
Applying the keys below in testing environments often but not always provided a significant performance boost to file copies.
Please make sure your Firmware and Drivers are up to date, if using a Dell server those should always be obtained from http://support.dell.com and not directly from the vendor.
More in depth performance guidelines references in this blog can be found at the following link. Windows Server Performance Tuning Guidelines
The Following 2 keys are more commonly used on client machines, however in server environments when moving large amounts of data between servers is a requirement these can drastically improve SMB/NFS file copy performance. Once the keys are in place you will need to reboot prior to testing.
This key was intended to help stabilize Windows File Shares in high latency environments, however with 10Gb CNA’s regardless of latency it can cause a performance hit on file transfers.
- DisableBandwidthThrottling
The default is 0. By default, the SMB redirector throttles throughput across high-latency network connections in some cases to avoid network-related timeouts.
HKLM\system\CurrentControlSet\Services\LanmanWorkstation\Parameters
\(REG_DWORD) Set Value to 1 to disable throttling.
The default is 1. By default, the SMB redirector does not transfer payloads larger than approximately 64 KB per request. Setting this registry value to 0 enables larger request sizes, which can improve file transfer speed.
- DisableLargeMtu
HKLM\system\CurrentControlSet\Services\LanmanWorkstation\Parameters
\(REG_DWORD) Set value to 0 to Enable Large MTU
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