tencent cloud

This document describes how to estimate the time for online migrating the system and applications from a source server in your IDC or cloud platform to Tencent Cloud CVM.

The migration time is subject to the data transfer speed during migration. You can estimate it by testing the transfer speed between the source server and destination CVM.

Estimating Migration Time in Different Scenarios

Scenario 1

If the destination type of a migration task is CVM instance, the estimated migration time is mainly the actual data transfer time.

For example, if the size of the data on all disks to be migrated on the source server is 50 GB and the outbound bandwidth is 100 Mbps, the estimated total migration time will be 1.14 hours as calculated below:

1. Convert the unit

• Convert the unit of the actual bandwidth to MB/s: 100 Mbps = 100 / 8 = 12.5 MB/s
• Convert the unit of the actual disk data volume to MB: 50 GB = 50 * 1024 = 51200 MB

2. Estimate the actual data migration time
   51200 / 12.5 = 4096 seconds = 1.14 hours

Scenario 2

If the destination type of a migration task is CVM image, the migration time includes the actual data transfer time and image creation time.

For example, if the size of the data on all disks to be migrated on the source server is 50 GB and the outbound bandwidth is 100 Mbps, the estimated total migration time will be 1.23 hours as calculated below:

1. Convert the unit

• Convert the unit of the actual bandwidth to MB/s: 100 Mbps = 100 / 8 = 12.5 MB/s
• Convert the unit of the actual disk data volume to MB: 50 GB = 50 * 1024 = 51200 MB

2. Estimate the actual data migration time
   51200 / 12.5 = 4096 seconds = 1.14 hours
3. Calculate the image creation time at a speed of about 160 MB/s
   51200 / 160 = 320 seconds = 0.089 hour
4. Calculate the total migration time
5. 14 + 0.089 = 1.23 hours

Relevant Operations: Testing Data Transfer Speed

You can use the iperf3 tool to test the data transfer speed, such as bandwidth and speed of data transfer from client to server.

Factors affecting transfer speed

• Outbound bandwidth of the source server and inbound bandwidth of the destination instance.
  For example, if the outbound bandwidth of the source server is 50 Mbps and the inbound bandwidth of the destination instance is 100 Mbps, the actual transfer speed won't exceed 50 Mbps theoretically.
• During the migration, the bandwidth isn't always fully used, and you can dynamically adjust the inbound bandwidth of the destination or relay instance.
• If the source server and destination instance are in different regions, the transfer speed will be lower than that when they are in the same region.

Note

• When you use online migration in the console, if the migration destination is a CVM image, the relay instance do_not_delete_csm_instance with a bandwidth cap of 50 Mbps will be created during migration.
• You can dynamically adjust the inbound bandwidth of the destination or relay instance in the console during migration to control the migration speed.

Speed test for migration to Linux CVM instance

For example, if you use the online migration feature in the console to migrate a server to a CentOS 7.5 CVM instance, you can test the transfer speed in the following steps:

1. Create a pay-as-you-go CentOS 7.5 CVM instance in the migration destination region.

   Note

   • If the migration destination is a CVM image, a CentOS 7.5 relay instance will be created during migration. To test its speed, we recommend you choose an available Standard model with a low CPU and memory configuration, which is more like the actual migration scenario.
   • The default port of the iperf3 server is TCP 5201. You need to add it to and open it in the inbound traffic configuration in the security group of the CentOS 7.5 instance.

2. Install iperf3 on the source server and in the testing destination instance respectively.

• Run the following command to install iperf3 in the destination CentOS 7.5 instance:

  yum -y install iperf3
  

• Install iperf3 on the source server. Use the installation command corresponding to the Linux distribution on the source server for installation.

3. Run the following command to start iperf3 in the testing destination CentOS 7.5 instance as the server:

   iperf3 -s
   

If "Server listening on 5201" is returned, the start succeeded.
4. Run the following command to start iperf3 on the source server as the client:

iperf3 -c [destination instance IP]

The returned test result is as shown below, indicating that the transfer speed between the source server and the test CentOS 7.5 instance is 111 Mbps.