Maximum I/O rates for attached HDD's on VMs - HYPER V or VMWARE

Hi there

I seem to have problems accessing FAST I/O times from Attached HDD's to a VM which is on the same LOCAL machine as the HOST.

I have a couple of FAST USB 3 devices which can transfer I/O decently fast.
These are attached to a LINUX VM as "RAW" devices from a Windows Host -- File system is XFS and these are attached as complete disks.

When sharing these with Windows - have to do it via SAMBA I can only get data transfer via the real Nic card which on a laptop will give a max rate of about 11 MB/s (11 megaBYTES / sec). -

Is there a way of getting the data to use the internal virtual NIC (which should be 1000 or 1GB/s). It shouldn't have to go via a wireless card for LOCAL data transfer !!!!.

Problem seems the same whether I use VMWARE or run the VM as a HYPER V machine.

HOST is Windows 10, VM is a Linux Guest. The attached USB HDD's work flat out even writing to or copying from an NTFS formatted external SSD attached to the VM - but when using Windows the rate drops to around 11 MB/s. !!!! as it's obviously using my LAN for transfer and using Wifi !!!!. I know it's using wifi as I can see the router going Bonkers with flashing lights for data transfer.

I must be doing something really stupid here but can't fathom out what.

Cheers
jimbo

cereberus said:

Well I just tried transferring a file from a 2nd hard drive on host to c drive in hyper-v guest and only got around 9 MB/s.

Hi there

It's also going through some sort of physical NIC card -- what should happen on local connections is that the I/O should go through a "Virtual NIC" which could treat the HDD's as locally attached devices -- for example a decent SSD attached to the machine via a SATA-->USB3 connector should be able to write a file to a LOCAL SSD (internal) at around 250 MB/s .

Perhaps our resident specialist @Kari has some suggestions here.

@Kari -- any ideas on getting full rate (or at least a decent rate) of I/O from a VM shared with a Windows HOST machine - i.e both HOST and VM on same machine - Host is HYPER V. My HOST has 2 physical NICS so perhaps from another machine on the LAN it would need to use a NIC but for the LOCAL machine it wouldn't need to use a physical NIC -- "Virtual switches or something".

I capture sometimes a whole slew of programs (1080p) from SKY Q - and want to copy these to a NAS server which I've replicated as a VM before building a physical stand alone one. The capture device only runs on Windows so copying 40 or 50 GB at 11MB/s is a pain.

(I can speed it up by copying first to a USB3 attached SSD and then attaching that to the VM, mounting it and copy the files but it seems a long winded way to go about this --we used to call this type of Network "Footnet" since it involved physically moving a device from one machine to another !!).

Cheers
jimbo

Kari said:

An easy way to increase transfer speed between a physical device and a Hyper-V virtual machine is to disable Virtual Machine Queue (VMQ) on your Hyper-V virtual switch. This can easily be done using PowerShell:

Code:

Set-VMNetworkAdapter –ManagementOS -Name "Name of your External Switch" -VmqWeight 0

You should notice an immediate increase in transfer speed as soon as you have disabled VMQ. I get transfer speeds between 60 and 80 MBps from an external USB3 disk connected to host to a VM on my laptops old 5400 RPM spinner. Not even close to USB3 max speeds but enough for me.

Another factor is VHD / VHDX disk type; transfer speeds are better using fixed size virtual disks on virtual machines than with dynamically expanding disks.

Although I have to admit I don't like this site in general, I have bookmarked this particular guide because it is a pretty comprehensive guide to understand Hyper-V vm speed bottlenecks: Troubleshooting Slow VM Performance in Hyper-V (Part 1)

Kari

Hi there

That did the trick

No wonder they call you the resident expert on this.

Just going into a Bar to watch Hull City vs Chelsea -- a goal fest for Chelsea I predict -- I think more people OUTSIDE the UK watch Premier League footie than in the UK -- besides in the UK you can't get the 15.00 (BST) games on Saturdays --no probs here.

Thanks again

Cheers
jimbo