Transfer Speeds Between Virtual Machines

[CardenComputers]

Hi

Had a search for this but cannot find anything..

I believe I read somewhere that the data transfer between 2 vm's on the same host travelled via the motherboard/hard drive and didn't travel through the network card to the switch then back again. How true is this? The transfer speeds I have seen in the past say otherwise. I am upgrading a server at the weekend and have a 140GB Exchange store that needs to go from one server to the other, if I could maximise this transfer then that would be ideal.

Any suggestions appreciated

Cheers

Dave

[weinstein5]

Welcome to the Community - If the two VMs are on the same ESXi host and connected to the same virtual machine port group and reside on the same subnet  the traffic between the two VMs will remain internal to the ESXi host 

[blipszyc99]

What kind of transfer speeds should we see then and what would limit the speed?  I have a Win7 VM and a Server 2008 R2 VM and when transferring a 2GB file from Win 7 to Server 2K8R2, I'm only getting 4MB/s.  If I transfer the same file from another Win7 PC (non-VM) to the same Server 2K8R2 VM, I get 40-50MB/s.

How can I troubleshoot this?

Message was edited by: blipszyc99 The Win7 PC and ESXi host are on connected to same Gb switch.

[weinstein5]

Are the two VMs on the same subnet? Are they on the same virtual switch?

[blipszyc99]

Yes.  Same Virtual Machine Port Group.  Same subnet. 

[CardenComputers]

I have to agree, I have setups where we have 4 servers all on the same vswitch and the transfer rates are slower than what I would expect copying across the network. Latest version with all of the patches.

Also for example when we are upgrading a server we always virtualise the old server first to the new box in the aim that transferring the data to the new server will be very fast onthe same vswitch and its safe to say this is not the case, copying still takes an age as if it was across a network.

[CardenComputers]

So here's the scenario, left a copy going overnight from one VM to another VM on the same vswitch. 13 hours it has copied about 60GB. This can't be right?

[LanczakB]

We're experiencing a similar issue with some of our VMs.  When two VMs reside on the same host (same subnet, dvSwitch, single vNIC) we see awful transfer speed (520 Kbps) whereas when one of the VM's is vMotioned to another host in the cluster network transfer speed increases to 37.3 Mbps.  Same network, 10gb switches backing, and ESXi 5.5.0 2068190 with 5.5.0 dvSwitch.  We've also migrated to separate clusters altogether and the issue remains the same; as long as they're on the same host they just struggle talking to each other for some reason. 

[CRODR]

I have the same issue. Whats the fix?

[farhanashraf85]

if i have a 1gig lan card connected with a virtual machine virtual switch , Two virtual machines are connected with the same virtual switch,

what default and max connection speed i can get between these two virtual machines ?

[vmkfix-SSA]

On below link to get some information about speed test between vm's.

https://vmkfix.blogspot.com/2023/09/how-to-check-speed-between-two-vms.html