Slow disk write between VM & Shares

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I have UnRAID & a Win10 VM that has very slow write speed from the vdisk to any shares, even with cache turned on on the share.

Vdisk is also on the cache (500GB Samsung EVO)

I only get 35-40MB/s max, but it ebbs & flows from max all the way down to stalling out completely.  Transfers usually look like rounded hills, ramping up, then fading to 0MB/s, then repeat. Sometimes it will start out at 150MB/s or more, but drops off rapidly.


Is this par for the course, or do I have something setup incorrectly? 

Would adding a 2nd SSD for the vdisk fix this? (should I pass it through or use unassigned devices?)

I followed gridrunners' setup suggestions pretty much to the letter & this is the 2nd or 3rd VM that has had this issue, I'm just now getting annoyed with it enough to do something about it.

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  • 9 months later...

I have slow transfer also I think it has something to do with the br0 network we emulate and passthrough to the VM... but it’s beyond me at the movement.... Even though I have a second 10gbe nick I can’t get it to work faster than 100MB/s where I should see something like 400MB/s going from my name to my SSD sata3 cache oboe share....

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  • 2 weeks later...

Hi Snidera,


I have the same problem. While the VM is working fine, any mounted shares from the array (could be nfs, sshfs or p9) are kind of capped at 35Mb/s. A test disk on that share from the server is totally fine (166Mb/s). 




Did you progress with that issue ? Any clue of what's happening ?


Thank you,



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  • 4 weeks later...

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