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
When the target of a Linux system migration is a CVM instance, the migration time depends on the actual time required for data transfer.
When the target of a Windows system migration is a CVM instance, the migration time depends on the time required to transfer the total disk capacity.
For instance, if the size of the data on all disks to be migrated on the Linux 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 actual disk data size to MB: 50 GB = 50 × 1,024 = 51,200 MB.
2. Estimate the actual data migration time
51200 / 12.5 = 4096 seconds = 1.14 hours
Scenario 2
When the target of a Linux system migration is a CVM instance, the migration time depends on the actual time required for data transfer and the time to create an image.
When the target of a Windows system migration is a CVM instance, the migration time depends on the time required for transferring the total disk capacity and creating the image.
For instance, if the total disk capacity to be migrated from your Windows system source server is 50 GB and the egress bandwidth is 100 Mbps, the estimated total migration time would be 1.23 hours. The steps are as follows:
1. Convert the unit
Convert the unit of the actual bandwidth to MB/s: 100 Mbps = 100 / 8 = 12.5 MB/s
Convert the actual disk data size to MB: 50 GB = 50 × 1,024 = 51,200 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
1.14 + 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
During an online migration via the console, if the migration target is a CVM image, a transit instance (named do_not_delete_csm_instance) will be created during migration, with a bandwidth cap of 50Mbps.
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, using the online migration feature in the console to migrate a server to a Tencent Cloud CentOS 7.5 instance. The steps for testing the transfer speed are as follows:
1. Create a pay-as-you-go CentOS 7.5 CVM instance in the migration destination region.
Note
If the migration target is a CVM image, a CentOS 7.5 relay instance will be created during migration. To test its speed, it is recommended to choose a standard type with lower CPU and memory configurations, which is closer to 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 the iperf3 tool on the source server. Please use the corresponding installation command for the Linux distribution of the source server to install the iperf3 tool.
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.
