[PVE-User] Speed problem

Luis G. Coralle luiscoralle at fi.uncoma.edu.ar
Tue Jun 2 14:25:50 CEST 2015

Hello everyone.

I have two VMs on a bridge ( eg vmbr3 ) that is not assigned to any
physical network card, that is, VMs are isolated on a LAN segment.

Both VMs have virtio bus, qcow2, virtio network card, 512 MB of RAM. At one
point, I start a scp 3GB file ( eg /var/www/image.iso ) to copy from VM to
another and transfer rate starts at normal speed and then extremely low to
360Kb/s or less.

Both virtual disks are housed in the same PVE, I tested both virtual disks
stored in /var/lib/vz ( ext3 ), in a stripped LVM 2 hard drives ( ext4 ),
in an SSD ( ext4 ) and the results were the same. I also tried to increase
the memory to 1024 MB to the VM and is the same.

The network speed tests between VMs without the intervention of the hard
drives ( iperf ) gives 6Gb/s.
The host is not very powerful, but it works very well, is a core i3 with
4GB of RAM. PVE version is 3.4-3  ( not clustered )

While running scp, I monitor the CPU and read/write disk of the host and
guests and was completely normal.
Is there some kind of priority for such operations? Is there anything else
I can try?


Luis G. Coralle
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