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SMB multichannel is a major advantage of SMB3. PowerScale OneFS 7.1.1+ supports SMB3 multichannel by default. Apple has introduced SMB3 multichannel support as of macOS 11.3+. Apple describes this functionality in the following KB article: Configure SMB Multichannel behavior.
SMB multichannel provides two features, failover between network links and additional throughput.
Testing for this paper indicates that failover works as expected in macOS 11.3+. A macOS client was configured with two 40GbE links to a OneFS file system (using an ATTO Thunderlink adapter). While the macOS client was playing back several streams of video from a OneFS storage volume, one of the network links was pulled from the switch. The video continued playing smoothly with few or no dropped frames.
However, when that network link was reestablished, the macOS client did not always recognize it. Usually, the network file system had to be unmounted, and the user had to log out and back into their account for the macOS client to reestablish the second link.
Multiple Ethernet connections to the storage only resulted in a small increase of aggregate throughput. Testing with 2x 10 GbE links to a OneFS file system showed approximately a 10% read improvement and a 20% write improvement. Testing with 2x 40 GbE links to the same file system showed little or no read and write throughput improvement. SMB multichannel support is new in macOS, and it is likely that over time the throughput benefits will improve.
The above Apple KB article on SMB multichannel behavior includes several /etc/nsmb.conf settings that impact how macOS uses this feature. Because SMB multichannel is enabled by default in OneFS, it is recommended to set macOS to use wired Ethernet links for SMB Multichannel. Using wireless connections for SMB multichannel could incur significant performance penalties.
To force macOS 11.3+ to prefer wired connections for SMB multichannel, add the following line to the /etc/nsmb.conf file:
mc_prefer_wired=yes
See Setting boot arguments in macOS in this document for more information about creating and editing /etc/nsmb.conf.