Macos – SMB slow read/write from Mac workstation vs. Windows

macosnetworkingsambasmb

We have an SMB share running in Hyper-V on Server 2012.

Read/Write to the share from Windows workstations on the network is around 100 MB/s, which seems good.

Read/Write from Mac workstations to the share is half this (50 MB/s) at best. Unfortunately these are the designers working with large files who actually need the network performance.

It's probably not a networking hardware issue, as iperf tests from my Mac to the server show over 117MB/s bandwidth. To clarify, this is an issue specific to using the SMB protocol from the Mac.

Best Answer

OK, I figured it out.

Running smbutil statshares -m /Volumes/MyShare/ revealed that the Mac's connection to the SMB share was negotiated using SMB1.

I then looked at ~/Library/Preferences/nsmb.conf and noticed that it contained the following:

[default]
smb_neg=smb1_only

After deleting this and running smbutil again, I can see the share is negotiating using SMB3.02, and the performance seems to have increased to where it should be.

Related Question