This topic describes the principles of server migration to help you better understand the process of server migration.
How it works
Server Migration Center (SMC) consists of the SMC client and the SMC console. This section describes the principles of server migration.
Migrate the source server to a custom image
You can migrate the source server to a custom Elastic Compute Service (ECS) image and then create an ECS instance by using the custom ECS image. The following figure shows the server migration process.
Migrate the source server to an instance
If you have purchased an ECS instance or a simple application server as the destination instance, you can directly migrate the source server to the destination instance. The specifications of the purchased destination instance must be compatible with those of the source server, such as the storage capacity and operating system. The following figure shows the server migration process.
Server migration principles:
Download and install the SMC client on the source server. If you import the information about the source server by using the CLI or the SMC console, the system automatically downloads and installs the SMC client on the source server. In this case, you can skip this step.
Run the SMC client on the source server. The SMC client submits the information about the source server to the SMC server by using the endpoint of SMC.
The SMC server creates a temporary intermediate instance and configures the security group of the intermediate instance to allow access to ports 8080 and 8703. If you migrate the source server to an instance, the destination instance is used as an intermediate instance. Then, the SMC server creates a temporary intermediate cloud disk and attaches the intermediate cloud disk to the destination instance.
The SMC client connects to port 8080 of the intermediate instance to establish communication and transmits the disk data of the source server to the data disks of the intermediate instance by using port 8703 of the intermediate instance.
The SMC server creates snapshots for the disk data of the intermediate instance and creates an ECS image from the snapshots. If you migrate the source server to an instance, the system disk of the destination instance is replaced by using the ECS image.
Supported network types:
SMC supports server migration over the Internet or a virtual private cloud (VPC). You must ensure the network connectivity between the source server and the intermediate instance or destination instance.
Server migration over the Internet: The source server must be able to access the Internet. The intermediate instance or destination instance must allow the source server to access ports 8080 and 8703. The data of the source server is transmitted to the intermediate instance or destination instance over the Internet. By default, this network type is used to transmit data.
Server migration over a VPC: You must connect the source server to an Alibaba Cloud VPC. The data of the source server is transmitted to the intermediate instance or destination instance over the VPC. You must specify a VPC and a vSwitch during migration. If a server in a self-managed data center, a VM, or a third-party cloud server can connect to a VPC in an Alibaba Cloud region, we recommend that you use SMC to migrate the server over the VPC. Compared with server migration over the Internet, server migration over a VPC is more efficient and stable. You can use VPN Gateway, Express Connect, or Smart Access Gateway to connect the source server to a VPC. For more information, see Connect a data center to a VPC and Migrate servers over a VPC.