Shared Folders virtio-9p performance issues

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Hello guys, I'm running a VM that is located on my SSD cache drive and has a few user shares mounted which are located on the array via 9p.

Mounting etc. works well, but I am experiencing very slow read/write speeds atm.


The shares perform well within Unraid (tested with around 150mb/s read/write) but as soon as they are used inside my debian VM the read speed of the uncached part significantly decreases to about 10-15mb/s.

Here is my fstab config:


backups /mnt/backups 9p trans=virtio,version=9p2000.L,_netdev,rw,msize=104857600 0 0


The msize entry already increased my write speed, but read speed is still very slow. Reading/writing to the VMs virtual disk is about 1200mb/s, so everything is fine with the VM itself. 

Has somebody experienced similar issues and has a clue how to fix this?

Edited by unifiedmamba
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So I've mounted the smb share via this guide without any further tweaking which results in about 135mb/s in the VM. Seems better, but not the optimal solution.

The problem now is that I still don't get full speed when downloading test files to my PC served by apache2. I now get around 50mb/s which is better than before but not the 115mb/s that are possible if I serve the file from a folder that is located on the qcow2 disk of my VM.

Additionally I have made bad experiences with the handling of small files by SMB which results in very very low speeds when transferring a few small files.
I would therefore like to fix the 9p mount to avoid the new problems that SMB could cause with my use case. 

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I too have spent the last few hours messing with 9pfs and have been seeing some pretty poor performance.


I use the following fstab options and get about 90MiB/s read and write (tested with fio and 4K block size; 128k and 256k saw slightly better performance)

epi_af /root/9pf_mount 9p trans=virtio,_netdev,rw 0 0


Adding 'msize=262144' or 'msize=524288' helps a tiny bit, epically with larger blocksize workloads


I too would rather not use SMB, but seeing as I get about 900-1100 MiB/s using SMB (which is almost exactly what I get to the virtual disk) I think that's what I think I'm going to go with, unless I can find a 9pfs solution.

Edited by Jawalking
  • Thanks 1
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After my perf testing, and reading through the following, I'm just going to use SMB for now.


Also looks like most of active dev work on virtio is for the Rust version ( I know the kernel is moving (perhaps including more that moving) that way, and fortunately for us unRAID keeps on a pretty new kernel, so perhaps we'll get to play with VirtIO-FS in 6.10:



  • Thanks 1
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  • 2 weeks later...

@Jawalking Do you think it would be a better solution to just create a new qcow2 or even raw image as a secondary drive and add all files that are now located in the shared folder into that one? Since I need the files to be very fast in the VM for nextcloud this sounds like a good solution for me. For use with other containers I could create a NFS share or something from the VM itself. Do you think this would work? 

Edited by unifiedmamba
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  • 3 weeks later...
  • 3 weeks later...
  • 11 months later...
  • 6 months later...

any new information here?  I'm maxing out at ~450MB/s with 9p.  Mounting with cifs gets me 1.1GB/s but then I run into needing to use sudo every time I need to create or a delete a file/directory.  What is the current "correct" way to do this so I have native speed when accessing my unraid shares from my vm without running into permission issues?

Edited by Aegisnir
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