Frequently Asked Question

Synology SMB3 Multichannel is enabled but file copies still use one network link. What should I check?

QUICK ANSWER

Two connected NAS ports do not guarantee a faster copy from one computer. SMB3 Multichannel needs a supported NAS/client configuration and usable network paths; it is different from Link Aggregation.

Applies to: Supported DSM/SMB Service and Windows or macOS clients. Exact model, package and client requirements must be checked before enabling the feature.

Draw both ends of the connection

Record each active NAS and computer adapter and its negotiated speed. A computer connected through one slower path remains a bottleneck. Include switches and USB adapters, rather than counting only NAS sockets.

Confirm the feature is supported

Check the NAS model, DSM and SMB Service versions and the computer's operating system. Multiple adapters or a suitable RSS-capable adapter are required. A single RSS adapter can distribute processing without creating a second physical link.

Separate multichannel from a bond

Review existing Link Aggregation before changing anything. Synology does not support using Link Aggregation with SMB3 Multichannel. A bonded interface and two independent SMB paths are not interchangeable configurations.

Check the SMB setting

On supported layouts, open Control Panel > File Services > SMB > SMB Settings > Advanced Settings > Others and check Enable SMB3 multi-channel. Record the previous state and use a maintenance window if active work could be interrupted.

Run a controlled comparison

Use the same computer, share and a sufficiently large test file. Observe network use at both ends while copying. Keep other heavy jobs out of the comparison and record whether storage, CPU or another link becomes the limit.

Check paths before adding changes

Mixed-speed adapters, routing and client behaviour can affect selection. Compare the observed paths against the intended topology. Ask for a review if the client never opens the expected connections; do not compensate by disabling security features.

Confirm the result

The intended supported paths carry SMB traffic during the same controlled transfer. Report observed throughput with its conditions; do not promise that two sockets double every workload.

Before going further: Do not break an existing bond or alter production VLANs without an access and rollback plan. Keep SMB authentication, signing and required encryption in place.

If you need help

Include these details in your ticket: NAS/model/software, client OS, adapter speeds, a simple topology and the before/after transfer conditions. Avoid including file contents.

Updated 261110