The speed of a VM cross-network copy is slow Highlighted

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This post is regarding the issue that the speed of a VM cross-network copy is slow. Please see below for more details.


Problem description


The virtual machine of the customer network belongs to two network segments: segment 10 and segment 192. The virtual machine network copy rate in the same network segment can reach 20MB/s or more, but the copy rate between virtual machines across the network segment is only 1MB/s.


Problem analysis


1. Firstly check the platform alarms. No IO delay exceeding the threshold alarm.

2. Troubleshoot the monitor of the virtual machine and host. All indicators are normal.

3. Test the virtual machines in the same network segment to ping each other and the virtual machines in the cross-network segment. The network is normal and no packet loss occurs.

4. Continue to test the ping between the virtual machines and the large packets. The packets over 4000 can connect to each other in the same network segment. The following figure shows the segment 10 and segment 192 and the large packets of virtual machines in the same network segment can ping each other.

ping

However, the large packets more than 4000 with cross-network segment cannot ping each other.


To check the cause of the cross-network segment failure, capture the packet on the host NIC. After analysis, the remote device sends 3 packets, but the destination end only receives 2 packets, resulting in the failure of the large packets on different network segments.

 

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Root cause


It is owing to the packet loss on the external network and the configuration check of the external switch is needed.


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