I have QEMU virtual machine. Linux host and linux guest.

I want stable and fast solution with minimal performance cost. I'm considering two technologies for shared folders (between guest and host): NFS and VirtFS (Plan 9).

There is small amount information on VirtFS from one side and there are some evidences that NFS isn't good option for virtualization from another side.

So my questions are following.

What is more reasonable for my purpose? What is more effective? What solution is consume less (speaking about CPU)? What solution is more fast? Are there some benchmarks on subject?

1 Answer 1


I have tried both and I am in fact running both in production environment.

My experience:

  • nfs is rock stable, of acceptable speed, but once the guest starts reading a lot of files or reading quickly a huge file, the host performance goes very noticeably down. This is especially pronounced if you run several guests and they start accessing the filesystem at the same time, and it takes forever to recover (since the data transfer speed drops to hundreds of KB/s and the guests continue reading the files). I had to introduce htb and fq-codel shaping and tune it a bit so that the host stays responsive.

  • plan9 is fast, however from time to time the virtfs-proxy-helper does not start at the first attempt. This makes automated startup tedious. Sometimes the filesystem just crashed and the guest becomes unresponsive, and I have not been able to find out why (big load, but only on some of the otherwise identical guests). There is also a lot of tweaking if you want to run vm as non-root and have full unix attributes in the guest.

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