Pingsutw
Contributor
Contributor

How to increase my Virtual Network Speed

There is question about network between different server,but i got a different situation.

I have two VM in a server,and I tried to test maximum network speed between two VM.

OS : CentOS

VSwitch speed : 10Gb/s (1.25GB/s)

Virtual network adapter speed : 10Gb/s

VM used VSwitch and Virtual network adapter to communicate,and there is no ethernet cable to impact network speed.

VM A : nc -l 20000 > /dev/null  VM B : time dd if=/dev/zero bs=100M count=200 | nc <VM A> 20000  
200+0 records in 200+0 records out 20971520000 bytes (21 GB) copied, 122.466 s, 171 MB/s 
real  2m2.479s
user  0m2.148s
sys   @@3m10.841s

The above command is used to test only network speed(not include disk read and write)

There may some communicate overhead in network.

I thought the network speed should be 1 GB/s,but why the speed is so slow.

What factor impacts the network speed or how can i speedup my network?

Thanks in advanced.

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13 Replies
MikeStoica
Expert
Expert

What type of adapter are you using? Do you have VMware tools installed?

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Pingsutw
Contributor
Contributor

VMXNET adapters,but i didn't install Vmware tools

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HassanAlKak88
Expert
Expert

Hello,

Kindly can you confirm if the type of this Virtual network adapter is VMXNET3 instead of E1000E.

Please consider marking this answer "CORRECT" or "Helpful" if you think your question have been answered correctly.

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Pingsutw
Contributor
Contributor

I make sure i used VMXNET3 adapter

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cernyj
Enthusiast
Enthusiast

Hello,

please try:

VM A: iperf -s

VM B: iperf -c <VM A>

Any diffrences in speed?

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Pingsutw
Contributor
Contributor

[ ID] Interval       Transfer     Bandwidth

[  3]  0.0-10.0 sec  14.3 GBytes  12.3 Gbits/sec

i user iperf i got 12.3Gb/sec

why it become more than 10 Gb/s speed

and what is different with time dd which i used?

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cernyj
Enthusiast
Enthusiast

Speed over 10Gb/s is ok, because you run both VMs on single server, so speed depends on your server HW performance and ESXi kernel settings.

About dd...I dont know. Maybe something with netcat.

Let's try to transmit some real data between your VMs and you'll see real (at least sequential) network speed.

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Dave_the_Wave
Hot Shot
Hot Shot

When you have vmxnet3 as a Network Device in your VM settings, you also need to install (preferably the latest version of) VMTools too.

To get a VM to work without the tools, there's the E1000 adapter for that, but it is "slower".

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cernyj
Enthusiast
Enthusiast

Is you CentOS 6 or 7?

7.X has more recent kernel 3.10 (now also pretty old, but 6.X use ancient 2.6).

You can just run "yum install open-vm-tools" (with EPEL repo enabled).

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Pingsutw
Contributor
Contributor

What should i do after i install VMtool,Ialready installed it,but the speed is same.

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Pingsutw
Contributor
Contributor

i use Centos 7.

after "yum install open-vm-tools" ,what should i do.

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MikeStoica
Expert
Expert

You can check your network speed now, see if it is improved.

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Pingsutw
Contributor
Contributor

no,it has same speed.any suggestion

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