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Poor CIFS/SMB performance on KVM Guest

Poor CIFS/SMB performance on KVM Guest

This is kind of stating the obvious. Running OpenMediaVault 0.5.48 as a KVM guest.

CIFS transfers from Windows 8.1 to OMV over gigabit ethernet maxed out at ~30MB/s.

Despite selecting Generic Kernel > 2.6 from within Virt-Manager, KVM defaulted to the virtual Realtek 8139 NIC.

Switching to the virtio driver mostly resolved the performance issues with CIFS transfers fluctuating from 60MB/s to 110MB/s.

Not sure what the source of the throughput fluctuation is, as it will be stable at 110MB/s for 10 minutes and suddenly drop.

I recommend using iftop on the KVM host to measure performance.